 If you liked
Kami to Sengoku Seitokai
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 ...then you might like
Yakuza Girl: Blade-jikake no Hanayome
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Protagonist starts off as a "newbie" but has latent god-like powers. He then wants to get involved with a mysterious, quiet, prodigy of a beauty which subsequently drags him into a dark plot that involves the school they go to, although the school aspect of the manga is seldom shown. The girl eventually gets interested in the protagonist's honest personality. There is ecchi involved in both.