Ottori Sousa

The story is about a Detective named Akiba who crosses paths with a High School Idol named Mizuho. He was assigned to protect her. But he's also a young detective and a bit unorthodox. For the first two volumes Mizuho ends up getting involved in Akiba's other cases but eventually it progresses into a friendship (and eventually a relationship??).
[plot synopsys from Baka-Updates]