Sensou ga Owatte Youzumi ni Natta Ningen Heiki no Kyonyuu Bishoujo wo Hirotte Ie ni Mochikaette Mitara

When his family decides to adopt a military-grade cyborg after the end of the war, Kento is skeptical -- I mean, she was trying to kill him just moments before! But will he feel the same when he discovers that the newly-docile Nina can serve... other functions?
(Source: Irodori Comics)
Note: A live-action AV adaptation (MIMK-098) was released on November 16th, 2021 and the second part (MIMK-111) on January 3rd, 2023.