If you're looking for manga similar to Triage X, you might like these titles.
Is it okay for a killer to love someone?... Even if that love has to be killed by her own hands...
A port town where the Mafia actively operates behind the scenes. Gohongi is a young man who has come back to this to place where he was born after many years and finds a job working at a video rental store, which also becomes his new home. It is here that he begins to live with a young girl named Mei and a homosexual by the name of Katsura. But both of them are members of the Mafia group, Lovely Town, and fifteen-year-old-Mei is a ruthless hitman.There have been rumors that the struggles between Mafia factions are becoming more intense, and still not able to completely grasp the situation, Gohongi winds up getting dragged into a world of trouble...
Sengawa's day job is as an accountant working for the police. But at night, he transforms into a ruthless assassin bringing death to anyone who deserves it. Those who have been wronged and whose grievances the police can't - or won't - listen to, turn to The Man With A Thousand Guns to avenge their suffering.
Teenage country bumpkin Tatsumi dreams of earning enough money for his impoverished village by working in the Capital - but his short-lived plans go awry when he’s robbed by a buxom beauty upon arrival! Penniless, Tatsumi is taken in by the lovely Lady Aria, but just when his Capital dreams seem in reach yet again, Lady Aria's mansion is besieged by Night Raid - a team of ruthless assassins who targets high-ranking members of the upper class! As Tatsumi is quick to learn, appearances can be deceiving in the Capital, and this team of assassins just might be… the good guys?!
Freesia is set in an alternative Japanese society that is at war, and has passed a law legalizing retaliatory killings. If somebody kills your loved one, you are legally sanctioned to kill, or hire someone to kill, the victimizer. The manga is set around a character who works for a firm that specializes in these retaliatory killings.
A story of pure vengeance, Lady Snowblood tells the tale of a daughter born of a singular purpose, to avenge the death of her family at the hands of a gang of thugs, a purpose woven into her soul from the time of her gestation.
GO TO HELL!! Join Yukito Yoji, professional assassin, on his conquest to rid Japan of its many scumbags! Corrupt politicians, evil doctors, selfish moneylenders...no one is safe in this over-the-top violence extravaganza!!
Mysterious assassin Mayo, a Japanese man in Malaysia, will kill anyone you want for just five dollars. Of course, he'll kill you for five dollars too, but doesn't that just even the score? With outcast allies at his side and formidable enemies against him, Mayo is the only one who can stop a conspiracy that stretches around the world!
Alice is a high school student who faces bullying at school and abuse at home by her uncle. One day, she witnesses her uncle being killed by an assassin called "Arachnid." Thinking that she'll be killed next, Alice has no choice but to fight back. Soon after, she wakes up at Arachnid's house, and he takes her in as his deadly apprentice.
Welcome to Kindergarten Noir, an exclusive school catering to children of the global elite. Rita, one of the teachers, has been on the hunt for a boyfriend but has had absolutely zero luck so far. One day, an assassin comes after one of the children...and he’s totally dreamy?! Dive into this action-packed rom-com as it unfolds inside the world’s “safest” kindergarten!