Somewhere in Japan, there exists a paradise where you can have a taste of all the forms of pleasure that this world has to offer. That place is Merian, the headquarters of the "Zenkoku Mesu Onii-san Federation" a.k.a "Zenmeren". It is the one and only meeting place for leaders from various fields to get their tired mind and body healed by a "Mesu (Female) Onii-san", namely men who have the grace of women and are specialists at healing the mind and bodies of men.
36 year-old Mikame is a platinum ranked Mesu Onii-san there and while he is overwhelmingly popular with the clients, he is growing tired from his creeping age and from dealing with obstinate regulars. One day, just when he was beginning to consider retiring, he had a fateful meeting with Harumitsu, a 26 year-old straightforward, single-minded and puppylike salaryman.
Even though Mikame tried to deal with him in an adultlike manner, after being on the receiving end of the latter's intense advances borne from his blinding youth and innocence, Mikame finds both his matured body and dried up heart slowly beginning to yearn for Harumitsu!!
