Photon Earth

The protagonist, he is extremely strong and fights using a quarterstaff made of black crystal. Has the word "baka" (idiot) scribbled across his forehead by Aun in black ink as he was trying to lead her back home. He's also able to withstand even the strongest blasts of Aho energy, even when its focused directly on him. It was later revealed that he was the source of the un-Aho, which is the reason why Aun's stasis field has no effect on him. Since he was angry at Aun for writing the word idiot in permanent ink, he inscribed the same word on Keyne's forehead, inadvertently marrying her in the process. Though he is simple-minded, he is very trustworthy and loyal to those he promises to protect.

(Source: Wikipedia)