Yuureitou

Yuureitou (幽麗塔, lit. "The Ghost Tower") is a manga series by Tarou Nogizaka. It was serialized in Big Comic Superior.

Plot
In the 1950s, an old woman was brutally murdered on the face of a clock tower by her adopted daughter. Two years later, the clock tower is known as the 'ghost tower' and it is supposedly haunted. Through an unusual series of events, a young NEET man named Amano Taichi is attacked by someone or something in the same clock tower, and finds himself bound to the clock face to be killed in the same way as the old woman. Luckily for Amano, he doesn't meet the same fate. He's rescued by a mysterious person who claims his name is Tetsuo.

Tetsuo is searching for a treasure that is connected with the ghost tower, and he wants Taichi to be his partner. Taichi, whose life has mostly consisted of poverty, loneliness, and pornography, is enticed by the idea of gaining extreme wealth. He's further convinced when a house fire leaves him without a home and depends on Tetsuo's charity. The adventure is going to be very dangerous, since the same 'enemies' who attacked Taichi before seem certain to try something again! Not to mention, Taichi really knows very little about his new partner, including "his" true gender!