Responses
http://www.mangago.me/read-manga/ai_to_yokubou_wa_gakuen_de/
the couple from ch.29+30, here´s the scene you described:
http://www.mangago.me/read-manga/ai_to_yokubou_wa_gakuen_de/mf/v06/c030/26/
Hehe! ThankZz!!!
It's a yoai manga I read a long of go, the uke have a cross on his back that the seme put on hem. Than the uke was going to cheat on the seme with a another man but he (the other man) stop when he sow the cross on the uke back. ٩(๑❛ᴗ❛๑)۶