Giichi (偽一, Giichi) is the deputy leader of the Mugai-Ryu along with Hyakurin under Habaki Kagimura in Blade of the Immortal. He was the first to be recruited and is also their most deadly member, having killed approximately sixty members of the Ittō-ryū by the end of the series.
The quiet, stoic member of the group who prefers to leave the outward leadership to Hyakurin, usually taking missions on his own without backup. His service to Habaki is both to work off his own death sentence and, due to an agreement with Habaki, to use part of his earnings to pay for medical treatment for his ill young son whom he had raised alone after his wife died years ago. Therefore he takes his job very seriously and interacts only minimally with the rest of the group, despite keeping a watchful eye on Hyakurin.
Despite being one of the most talented fighters of the series with an impressive body count, he is somewhat cynical about his occupation. He takes little pride what he deems 'underhanded murder' despite his enjoyment of the hunt, and remarks that people seeking to gain power or become the best at something need to lose something in return, often the things they love the most - a foreshadowing the proves unfortunately true for many characters in the manga.
Giichi has a deep-seated drive to have a purpose and a job to do, one which occasionally borders on self-destruction. When he earns his freedom (in an unfortunate twist of fate, on the very same day his son dies) and realizes that for the first time in his life he is suddenly under no obligation to anything or anyone, he has no idea how to cope and ends up in a remote beggars' camp trying to drink himself to death. Eventually, Hyakurin finds him and, in a rare moment of emotion, he breaks down and admits he doesn't remember how to live like a normal person anymore and considers a life of his own worthless.
Relationships with other characters
Hyakurin: Giichi is not shown to be truly close to any other characters except for Hyakurin, for whom it is implied he has some sort of unspoken affection. When she is captured and tortured by a group of vengeful Itto-Ryu, he tracks them down and after violently executing all but one (whom Hyakurin herself summarily dispatches), takes care of her while she recovers. After he earns his freedom from the shogunate, he attempts to buy hers as well from Habaki with the entirety of his significant payout and appears devastated when Habaki refuses. Eventually, Habaki agrees to let her go on the condition that Giichi brings Manji in.
Hyakurin, suspicious upon finding out that her debt has been mysteriously paid in full and Manji nowhere to be found, eventually tracks down a drunk and now severely depressed Giichi, and tries to knock enough sense into him (literally and figuratively) to get him back on his feet. After he realizes Hyakurin is pregnant due to her rape at the hands of the Itto-Ryu thugs who captured and tortured her, he manages to convince her not to abort it and promises to raise it himself. This prompts a quiet "I love you" from Hyakurin, but Giichi either doesn't seem to hear it or doesn't seem to know how to respond to it. However, from then on he and Hyakurin are inseparable despite their clashes of personalities and priorities. In the end, it is presumed they will raise the child together and attempt to start a normal life.
Rin: Giichi is hesitantly helpful to Rin and seems to respect her dedication. When he discovers her sneaking out to track down Anotsu, he passes along the intelligence he had acquired as to where he might be In Kaga and, rather than stopping her, tells her to be careful and allows her to leave.
Habaki: Giichi has a great deal of respect for Habaki and considers him the person who made it possible to keep his son alive (despite the inevitable futility of the agreement). In keeping with this, even after his release from the group, he feels obligated to help Habaki in any way possible.
Manji: He seems to regard Manji with frustration due to the latter's cavalier attitude, particularly during their spat when Giichi tracks him down to bring him to Habaki and later when they team up to go to the quarry to rescue Rin.
Weapons and fighting skill
Giichi's greatest advantages are his speed and ability to improvise. He is also an inexorable, determined fighter who keeps coming no matter what wounds have been inflicted - as shown in the showdown at the quarry and his brutal fight with Abayama - and by the end of the series is one of the most physically scarred survivors. According to Mitake, he is the only one who could potentially kill Anotsu outside of Habaki himself.
His main weapon for most of the series is Kanetsura's Mito-No--Kami: "Guardian of the Three Paths", a circular blade constructed like a handcuff attached to a long chain. The main blade sharped on both sides and the moving, hinged blade sharpened on the inside. He uses both the chain and the guillotine-like blade to attack from a distance, either to disarm the enemy or sever limbs or heads. After Manji breaks it, he uses a pair of sickles attached by a chain.