Seiichiro Tatsumi (巽 征一郎,Tatsumi Sei'ichirō?), voiced by Walter Pagen in English, and Toshiyuki Morikawa in Japanese, is the secretary of the Shokan division. In addition to this position, which allows him control over department finances and thus substantial influence over Chief Konoe, he is seen to partner with Watari when working on a case. He also assists Tsuzuki and Hisoka on multiple cases.
In volume 5 of the manga, it is revealed that Tatsumi was Tsuzuki's third partner. This only lasted for three months until Tatsumi quit, unable to handle Tsuzuki's emotional breakdowns which paralleled those of his mother, a well-born woman whose death he blames himself for. His relationship with Tsuzuki, though partially resolved in volume 5, remains uncertain and often underlaced by guilt (on Tatsumi's part) over their past partnership and protectiveness. However, petty conflicts often arise over issues with department finances, most particularly in the cost of rebuilding the library after Tsuzuki destroys it (twice).
In addition to the standard abilities of shinigami, he also has the ability to manipulate shadows both as weapons and as a means of transport.
Tatsumi messing with Tsuzuki about his sweets addiction
Tatsumi getting something off of Tsuzuki's face.
Tatsumi caring for Tsuzuki after the Devil's Trill Arc.