Coming
Sequel http://www.mangago.me/read-manga/come_over_1/
Come Over
Sequel to http://www.mangago.me/read-manga/coming_1/
Mujaki na Wanko to Nekokaburi
Must be an older work, illustration style is different from Niyama's usual.
Boku no Omawarisan
Niyama always write about age-gap couples: older uke and young seme Summary Seiji Tajima is a single, forty-something shop owner who's close friends with police officer Shin Nakamoto. Shin, who's just been assigned a patrol in Seiji's neighborhood, has known the older man since he was in high school - back when Seiji himself worked in the police force. Shin's harbored a crush on Seiji for years, but has convinced himself that their relationship is as good as it gets - until one day out of the blue, Seiji casually mentions the possibility of trying his luck with men...
Sonna ni Iu Nara Daiteyaru