Tatsumi's background is horribly undefined in canon, but we do know a little bit. His mother, who was from a noble family, eloped with his father, and gave birth to Tatsumi and his sister. His mother made a rather bad housewife, however, and Tatsumi ended up helping and protecting her (most likely, this is the point he learned how to cook, which he is very skilled at). Perhaps the most important thing we know from his childhood is that every memory of his mother Tatsumi has is a sad one, and Tatsumi believed he was responsible for this sadness, and her constant crying. Ultimately, Tatsumi kills his mother, though we do not know why, or even how old he was when it happened.

Then, an undetermined amount of time later...he dies! We do know he's 29 this happens, however.

Tatsumi is one of the souls chosen to becoming a Shinigami for JuOhCho, or the organization that judges the souls of the dead. What we see the Shinigami doing most in the series is investigating cases of people who haven't died yet, but should have, or cases where a notably high number of people have been killed, most often with supernatural elements. Tatsumi starts off his afterlife career doing these investigations, and at some point (again, not revealed), becomes Tsuzuki's 3rd partner. The partnership only lasts three months, but is still long enough for Tatsumi to develop very strong protective feelings towards Tsuzuki, largely because the man reminds him of his mother. However, this also flips Tatsumi's angst switch, and he puts an end to the partnership once he realizes that he can neither be the support Tsuzuki needs, nor keep himself together while watching Tsuzuki fall apart.

How much longer Tatsumi remains an active Shinigami is, once again, unknown. What we do know is that it has been at least 50 years from the point I am taking him (just after the Kyoto Arc) since he has directly worked on investigations. Instead, he has served as his department's secretary, and second in command--though there is speculation that it is Tatsumi who really runs the show...with an iron fist, no less. Tatsumi is responsible for balancing the books, which he takes extremely seriously. He also helps assign cases to particular Shinigami, cooks, and waters the plants in times of stress.

There are times, however, when Tatsumi will become directly involved in an investigation. If he is present and there is a reward offered (for minor things), or if Tsuzuki is involved and potentially in danger. Such is the case during an investigation in Kyoto, where Tatsumi arrives to fend off Muraki's attacks. Tatsumi actively becomes involved at this point with protecting Mariko, a girl who witnesses this battle, and who Muraki has said he will kill. The girl is still kidnapped, however, but only held captive for a short time before she is returned, injured, to Tsuzuki and Hisoka.

Mariko is brought back to Meifu (the world of the dead) to recover, and Tsuzuki decides to stay at her bedside during the night. What no one knows, however, is that Muraki has already warped Mariko into a monster. She tries to kill Tsuzuki, but is killed by one of his shikigami instead, much to Tsuzuki's protest. Tatsumi, along with Hisoka and Watari, find Tsuzuki trying to heal Mariko's severed head by licking it clean. Muraki shows up at this point, and kidnaps Tsuzuki, who has fallen into a catatonic state.

Tatsumi, Hisoka, and Watari try to find where Muraki is holding Tsuzuki, and after a confrontation with Oriya, learn the location. By the time they get there, however, Tsuzuki has woken and summoned one of his shikigami to kill both himself and Muraki. Realizing Tsuzuki's wish to die, Tatsumi almost lets him, but in the end employs his shadow powers to save both Tsuzuki and Hisoka, who has gone into the flames of the shikigami to try and rescue Tsuzuki.

Everyone returns to Meifu, and after a recovery period, Tatsumi talks to Tsuzuki about the man's desire to die, questioning whether he should have rescued them. Tsuzuki (and later, Konoe) reassures Tatsumi that what he did was indeed right, with Tsuzuki thanking Tatsumi for rescuing him. After this point, things seem like they will return to the normal routine for a bit, with typical investigations leading to a masquerade party held by the Earl in the Hall of Candles. The Earl offers Tsuzuki relief in his words, which is later told to Tatsumi and the others. The Earl also asks Tatsumi, Hisoka, and Watari to be by Tsuzuki's side whenever the man may need, which is easy enough for them to promise. By this point, I think that Tatsumi's feelings over Kyoto have resolved, and he'll go to bed that night feeling relaxed...and this is where I am picking him up at.