In short terms, there is some kind of disease or illness that the (Sogino koichi-san) main character has. He has to take pills to keep his illness or disease in check. I guess when he see the other guy in the store he goes to, I guess his hormones start to kick in and his body starts to get heated for him. They have sex and his disease and or illness starts to effect the other guy in the store, when they we're in the bathroom. That's all I have from reading it!
Not quite! The MC is Hinoki-san, who just went to the hospital and was diagnosed with the Pheremone Hypersecretion illness. He went to get treated because he was getting aroused whenever he was around the bento guy, Sugino Kouichi. He assumed Kouichi desired him, because others' desire triggers arousal in people who have the illness. When they were getting freaky in the bathroom, Kouichi (bento guy) showed MC his own medication - he has the same illness, and kept getting aroused because of Hinoki-san's desire. So basically they BOTH have it and have been triggering each other, which is so sweet really, it's mutual!
It is not an one-shot. There are more chapters.
I don't understand this, I'm sorry ╥﹏╥ I'm not dumb I promise ┗( T﹏T )┛ but care to explain anybody?