This article contains spoilers for Golden Kamuy story. Please read at your own risk.
Tsurumi's most distinguishable physical trait is a porcelain enamel plate that covers his forehead, with brain fluid leaking out sometimes. He has his hair slicked on the back of his head and has a handlebar moustache and goatee. He is of average height and has a muscular, lean build.
Tsurumi usually wears his officer uniform with a coat to protect himself from the cold. On a few occasions he was shown to wear a quite unusual shirt made of the skin of tattoeed convicts.
|Spoiler warning: Significant plot details follow.|
|As Kouichi Hasegawa, Tsurumi sported a buzzcut hairstyle and wore round glasses. As an outwear he would wear a furry coat, a pair of boots; he would also carry some of his photography tools in a handbag and a briefcase. While at home, Hasegawa wore a dark vest over a light long-sleeved button up shirt as well as traditional Russian bast shoes (lapti).|
|Significant plot details end here.|
Ambitious, mysterious, erratic, histrionic and slightly eccentric, Tsurumi is a unpredictable man, even to his own followers. However, in the past, Tsurumi was more normal and even a brave Japanese officer who fought at the front during the Russo-Japanese war.
Receiving a shrapnel in the head and the general bitterness at the poor treatment his division has received after the war has made Tsurumi psychotic and violent, though his manipulative tendencies have already been present even before the injury, having manipulated most of his current subordinates into joining him. It's unknown whether he already had sadistic tendencies back then or not, as Tsurumi before his injury in the flashback clearly didn't want so many soldiers to rush mindlessly into war to be killed, but when he recalls the war, he states how the skies poured with blood of the fallen soldiers was one of the most perfect sights he'd ever seen.
He is prone to threatening people and personally inflicting physical injury on his enemies but hides his brutal tendencies under a veneer of sophistication and sympathy. Tsurumi doesn't care whether someone is his ally or foe once they did something he didn't like, such as he bit Captain Wada's finger off and had him killed when feeling insulted by him. He also genuinely admires the macabre work of Edogai and develops a friendship with him. Tsurumi never becomes angry, but coldly manifests his rage with a brutal gesture, perhaps due to his brain damage. Tsurumi mentioned once that he has trouble controlling his temper ever since the brain damage, showing that he's self aware and sometimes uses his brain damage as an excuse of his actions despite that. Although not being able to show normal emotions since the brain damage, he suffers from mood swings as well as sudden outbursts of violence and leaks more brain ooze than normally when dealt with certain emotions.
Tsurumi aims to take over Hokkaido and is very ruthless in his methods. He kills anyone in his way or threatens his plan. He seems to still hold the men under his command in high regard but hates traitors. He has shown a level of care for his subordinates as seen when he tries to get Nikaidou to eat his food and provide prosthetic limbs for him.
Tsurumi is also a very charismatic and manipulative man that can sway the minds of other people with a powerful and explosive speech. As a result, he is not above lying to other people if it is to get what he desires, such as loyal and strong followers, Tsukishima for example who Tsurumi lied to for 9 years and had him study Russian in order to become an interpreter just to get him out of death row, recruit him into the 7th Division, and make him one of his loyal followers.
|Spoiler warning: Significant plot details follow.|
|Under the identity of Kouichi Hasegawa, Tsurumi was a humble and compassionate man who loved his family and was also kind towards strangers who had come to him for help. He was also a very observant man as he easily noticed how other people would behave and any other unique traits that they displayed. When the Okhrana (secret police force that cracked down on revolutionaries and anti-governmet elements) found out about him, a worried Tsurumi told his wife that she should go back to her family home, stay there and absolutely not return until he comes to get her, knowing that she wasn't safe if she had stayed with him, showing that he truly cared for her despite being a spy. Though they were part of his guise while on a spy mission, Tsurumi genuinely seemed to care about his family as he spent time with them in their final moment and became disillusioned with the Japanese government as a result of their deaths.|
|Significant plot details end here.|
- Charisma: Tsurumi is highly manipulative and can convince others with his sweet lies or a powerful speech.
- Intelligence gathering and analysis: Tsurumi is regarded as a dangerous man for has proficiency in the intelligence discipline, as well as his sharp might and
- Physical strength and agility: Tsurumi is shown to be physically strong, as he snapped a incoming cane with one hand. He is also quite agile as when he pursued Sugimoto and his horse was shot down by an arrow, he did a barrel roll and immediately kept pursuing Sugimoto on foot.
- Russian language: As part of his duty as a spy in Russia, Tsurumi is also fluent in the Russian language.
- Taxidermy: Even before meeting Edogai and learning from him, Tsurumi was interested in taxidermy (as evident by the shirt that he made from Matsuo Tsuyama's skin). It is possible that he was the one who preserved Wilk's skin.
Throughout the events of the series, Tsurumi has been shown carrying different arms, including:
- Borchardt C-93 (holds 8 rounds)
- Colt Model 1903
- Winchester Model 21
- Winchester Model 1897
- Type 38 Machine Gun
- (To Wada) "A warrior takes pride in his scars. In fact, wouldn't you say it makes me look rather dashing?"
- (To his soldiers) "Our war is not over."
- (To Sugimoto) "I'm your Shinigami. Your life is a candle, and I can blow it out anytime I choose."
- (To Sugimoto) "Even if your life's candle is an immortal flame that can never be blown out... All I have to do is bite the candle down to nothing!"
- The "篤" kanji in Tsurumi's name can mean "fervent", "kind", "cordial", "serious", while the "四" kanji might indicate that he's the fourth son in his family.
- The mangaka Satoru Noda based Tsurumi's background on Hasegawa Tokushirou, the grandfather of Noda's father's friend who shared the same name, Noda Masanobu. After Tokushirou passed away, his relatives found a couple of curious things within his possessions: an old résumé and a child’s pinky bone. 
- Before the fanbook confirmation, there were other speculations about Tsurumi's character real personalities inspirations:
- Toshiro Mifune, a famous Japanese actor from Niigata who also worked in the photography shop while he lived in China. 
- Ishimitsu Makiyo, a member of Japanese Imperial Army and an intelligence officer who worked undercover in Siberia and Manchuria.
- The real-life Hasegawa Koichi, a Niigata photographer; however, information of him is sparse.
- Sumi Shinchirou, who lead the 26th Infantry Regiment of the 7th Division. 
- Pier Luigi Bellini delle Stelle, an Italian anti-fascist partisan and practicing lawyer, notable for capturing Benito Mussolini at Dongo in April 1945. 
- Tsurumi likes Japanese sweets (Wagashi) but dislikes alcohol.
- In situations where he has to drink with his superiors, Tsurumi only pretends to drink and get drunk. It's because he is a lightweight and has low tolerance for alcohol.
- Tsurumi is often the subject of many references and homages to different works of fiction:
- The quote Tsurumi said towards Sugimoto about being his Grim Reaper, capable of blowing his 'candle of life', is a reference to a Rakugo story titled Shinigami.
- The gestures he did in Chapter 31 while giving a speech were identical to those of Adolf Hitler in Triumph of the Will.
- In Volume 6 omake, Tsurumi plays Ludwig van Beethoven's Piano Sonata No. 23 in F minor, Op. 57, also known as the Appassionata. 
- The way Tsurumi enters the house in Chapter 105 is a reference to a scene from the movie Léon: The Professional.
- The scene in Chapter 107, where Tsurumi cradles the baby as Nikaidou, Tsukishima, and Koito look on at them is a reference to "Song of the Angels", an 1881 painting by the French painter William-Adolphe Bouguereau.
- In the scene in Chapter 136 where Tsurumi fires the gun, the line "Come and say hello to Arisaka's little friend" is a reference to a quote from the movie Scarface.
- The way Tsurumi is holding the deceased Usami in his arms in Chapter 256 is a reference to Michelangelo’s famous sculpture of Jesus laying in the arms of the Virgin Mary, the Pietà.
- The flowers, which are sometimes seen behind Tsurumi in scenes and panels, are opium poppies. Tsurumi oozing brain liquid is reminiscent of opium poppy seed pods exuding latex.
- In 2018 Golden Kamuy All-Stars popularity poll, Tsurumi ranked 7th, gaining 5,499 votes. 
- When asked what occupation Golden Kamuy characters would have if they lived in the present time, Satoru Noda said Tsurumi would be a Public Security (Intelligence Agency) officer.
- According to Golden Kamuy anime character reference sheet, Tsurumi's height is 173 cm (5'8). 
- Tsurumi plays with his headplate while bathing. 
- Tsurumi is shorter than Sugimoto, Toni, and Wilk, same height as Koito, and taller than Edogai.
- Tsurumi is lighter than Sugimoto, Tsukishima , and Vasily, and heavier than Toni.
- Tsurumi's favorite gun, Borchardt C-93, was brought to him by Arisaka from Germany on his request.
- In the magazine version of Chapter 7, Tsurumi's appearance used to be different: his headplate was of more angular shape, his eyes were light instead of dark, and his facial hair was trimmed shorter. It was later changed in the volume version.
|7th Division Members||Hajime Tsukishima • Kazuo Maeyama † • Kennosuke Mishima † • Kouhei Nikaidou • Mokutarou Kikuta † • Otonoshin Koito • Tokishige Usami † • Tokushirou Tsurumi • Youhei Nikaidou †|
|Deserters||Fumio Okada † • Genjirou Tanigaki • Houzou Tamai † • Hyakunosuke Ogata • Ikutarou Komiya * • Naoaki Noma † • Rikimatsu Ariko|
|Allies||Heiji Koito • Hidenobu Okuda • Narizou Arisaka • Teruchika Yodogawa • Yasaku Edogai †|
|Associates||Kouji Wada † • Koujirou Hanazawa † • Yuusaku Hanazawa †|