Koishiki Kaikyuu

Sgt. Akasaka, a college graduate, who enters the army after passing the high level exams is raped by LP Oohori. LP Oohori is a solider who is younger and of a lower rank than Sgt. Akasaka. LP Oohori was tasked with teaching Sgt. Akasaka about his unit.

However, after Sgt. Akasaka advises LP Oohori to take the army examine, Oohori gets angry and rapes Sgt. Akasaka. For reasons unbeknownst to LP Oohori, Sgt. Akasaka doesn’t report the assault. From this point on Sgt. Akasaka is continuously sexually assaulted by LP Oohori as “payment” for his lessons but is the sex only payment for LP Oohori or something more?

(Source: Mangafox - By Backlash67)