Busō Renkin Odcinek 11: Two People Separated By Death

Shusui recalls his earliest memories: being abducted by a woman claiming to be his mother and the days he spent in confinement. The twins grew up never questioning the closed world they lived in. Eventually, their "mother" died and the twins were rescued from near starvation and taken in by Dr. Butterfly. Since then, both sister and brother have only wished to live together for eternity as a homunculus. When Tokiko tries to kill off the twins, Kazuki pleads for their lives because they are still human.