Arakawa Under the Bridge

Gag manga about a young “elite” man who has a policy of not being in debt to anyone. But he ends up owing his life to a strange girl who saves his life. Nino, the girl, believes she is from venus & lives under the bridge by the Arakawa river. So the young man ends up living there too.
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Ichinomiya Kou has always lived according to the creed of his wealthy, successful family: never be in debt to anyone. But one day, under the Arakawa Bridge, his life is saved by a homeless girl named Nino. In order to pay her back, Kou promises to be her boyfriend; and thus begins his new life under the bridge.