A boy transfers into an academy where individuals possessing a special power known as "Soul Shell" gather.

The transfer student's name is Yuuma Nanasaki.

Most who possess this power can manifest their Soul Shells as weapons or armor.

However, Yuuma could only manifest his Soul Shell on his right hand and left leg.

He can't even manifest weapons.

Nevertheless, Yuuma demonstrates overwhelming combat prowess without relying on his Soul Shell.

The true identity of this Yuuma, however, was a person whose name, age, and entrance data differed from the records.

His real name is — Genjuro Magara.

He is the man who once made a name for himself as a legendary mercenary before suddenly disappearing several years ago.

When the "King of Flies" steps into an academy for boys and girls with special powers, borrowing Yuuma Nanasaki's body to act as a certain girl's bodyguard — the world begins to stir once more.

This is the story of the strongest man, once known as "Beelzebuth," surpassing even the strongest.

*Main story concluded.