One Piece: Starting by Snatching the Dark-Dark Fruit

Kudiria Noki, son of a Navy martyr, a once-in-a-century genius, is stunningly beautiful and deeply favored by the women in the military.

At a young age, he already knew admirals and vice admirals, earning him the title of the Navy's ultimate insider.

He is a close friend of Admiral Aokiji, the nephew of Akainu, and the life-saving benefactor of Chief Instructor Zephyr...

Such a person, at the graduation exam of the Navy Elite Academy, grabbed the Dark-Dark Fruit, which is famed as "the most evil ability in history".

(Note: This story has no system, the male lead is not effeminate, has a mature mindset, is decisive and ruthless, female characters are mostly supporting roles, definitely not a mindless harem story, the early part is a bit slow-burn, and the protagonist's goals will gradually come to light.)