This one makes you flinch every time somebody smiles. Sheena is the one girl in an orphanage full of trained killers who still wants the war to stop, which means she spends thirteen episodes being the softest thing in a building that manufactures weapons out of parentless girls. Then her roommate dies, and she meets a stranger standing in the blood with a smile on her face, and the show quietly tells you exactly what kind of love story this is going to be. The romance isn't decoration here, it's the entire engine, and it runs straight at the tragedy instead of away from it. Death is routine to everyone in this place except her, so every attachment she forms reads like a countdown. Bring the tissues, then sit with the fact that the title told you up front.
Sheena grows up in an orphanage designed to forge children into killers, a place where death is routine and mercy is a liability. But Sheena wants no part of this life. She dreams of peace in a world built for violence. Everything changes when a bloodstained girl appears during the orphanage's darkest hour, smiling serenely while chaos erupts around them. The next day, that same girl enrolls in Sheena's class under the name Mimi, and rumors spread quickly: she's the facility's ultimate secret, an immortal warrior who cannot die. When Mimi becomes Sheena's assigned roommate, their connection deepens into something neither expected. As Sheena discovers more about Mimi's impossible nature and tragic past, she finds herself drawn to someone who has watched centuries pass while remaining untouched by time's weight. In a place built to destroy love, these two girls begin to ask if happiness is possible for weapons like them.