Taku and Mutsuki are friends who no longer talk as much as they used to when Mutsuki gave Taku a brush off. A year later when their parents go on vacation and Mutsuki is left to look after Taku, Mutsuki slips Taku a few mysterious pills that put Taku in a "agreeable" mood.
A man known as the Messiah whose tongue technique is said to heal impotence takes up a job to heal a nervous-looking man, but is quite surprised by the turnout.
Sequels-
Messiah no Kyojitsu
Messiah no Sentaku
Himitsu no Okusuri