Nezumi no Hatsukoi

Nezumi is a girl who was raised as a hitman by the yakuza and grew up not knowing human love. An ordinary young man, Ao, knows nothing. They fall in love and start to live together, but the evil hand is close at hand...
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Read the prequel oneshot featuring Messiah-chan's backstory [here](https://mangadex.org/title/a53ff4b3-1514-4b91-9fa0-acd99dd797de/gomennasai-messiah-chan).