Tsume Ato

Main character lost his memory in a traffic accident. He now wakes up in a pavilion of a mysterious fantasy novelist active during Showa era. He is greeted by manager Misako who requests him to counsel two girls and recover memory this way. He spends more and more days here, but the memory does not return! One day a letter with threats arrives at the pavilion, followed by a phantom "golden mask" that causes mysterious disturbance. And at this point memories of his ugly past gradually start to return.

[From vndbreview]