Dandadan, Vol. 15 (manga)

Now that the alien invasion has been thwarted, Okarun and the others start a research club with the goal of finding his missing family jewel. As they prepare to get their new club up and running, they can't help but feel suspicious of their assigned advisor, Mr. Sanjome, of whom they strangely have no memory. Soon after, Okarun's class rep reveals to him that ever since she picked up a gold ball, he's looked like… a handsome vampire?!