Responses
I think it could be this one
http://www.mangago.me/read-manga/souteigai_love_serendipity/
Oh yes! That's it, thank you!! (≧∀≦)
First chapter has a couple that's already been going out for a few years. The uke believes that they may have lost their spark so he gets sex advice from his coworker, toys too i think. When they try out s and m the seme is the m and ties the rope on himself. The second couple is about the coworkers from the first chapter, involving a goukon and love hotel