Commander of "Black Lizard"
Tachihara is a slightly imposing boy with short, spiky brown hair and small amber eyes. He also has a bandage going across the bridge of his nose.
His normal outfit consists of a long-sleeved and rather baggy white v-neck shirt with the border being black and the left sleeve rolled up so it isn't visible.
This shirt is partially covered by a military green crop jacket that has beige fur around the collar. He also wears dark blue pants, brown boots, and a black band on his left wrist.
He is shown to be an impulsive and rash individual, which is proven by how quickly he is to solve issues using his twin guns without careful thought for other strategies. His on and off fights with Gin Akutagawa are almost always instigated because of his short temper, regardless of whether he's the one who did the first move or not.
His loyalty to the mafia isn't clear, but his regard of Ichiyou Higuchi as an older sister is reminiscent of how most young mafia members regard their female higher-ups as such; a possible implication of his attachment to his work.
Despite the way he presents himself as a strong and rugged person, it all crumbles down when Atsushi Nakajima put the safety of a nearby child in his hands during the events of Chapter 29. He's seen to be in a slight panic over what to do with what was presented to him while he stutters his words because of the sudden crying the baby's been doing. It's not known what could have happened if he had taken care of the infant, since the rest of the Black Lizard show up along with Higuchi.
His demeanour is broken down even more when Tachihara shows how on edge he is as he was overhearing the "relaxed meeting atmosphere" the Mafia's executives have presented the day he was on guard duty; breaking into sweats as they chat more.
As seen in the background of Chapter 41, Tachihara sometimes assists in Elise's shopping trips; carrying around her load of boxes without spitting out a single word, probably to finish this up quickly since he was stunned by her putting a bow on his head. Surprisingly, he didn't yell at the guards beside them, who were smiling and laughing at his situation.
Tachihara despises being belittled, which is the prominent reason why he's mostly bold with his actions, though it's his downfall. In Chapter 48, he was referred to as a "small fry" by Junichirou Tanizaki, to which Tachihara responds by squeezing his gun's trigger with no thoughts over if Tanizaki was baiting him or not.
Later on in the chapter, he outbursts after Tanizaki escaped on how he and his team should've padded him down first; proof presenting how much less he thinks with his brute strength when not in the moment of action.
Tachihara doesn't possess an ability, but he owns twin guns that are his main choices of weaponry.
There isn't anything currently known about his past or what led him up to being a member of the Mafia, although, his hinted at comfort with Ryurou Hirotsu could be an indication on his history with him or the Mafia.
- In one of the first rough character sketches for the Black Lizard, Tachihara's black band had a smiling face on it.