Yoshi is an 18-year-old boy with a dim future. Despite his serious illness, he can't complain so much after his enrollment to the Yamaku. At least, he still has a girlfriend, friends, and wealthy parents. No worries and no responsibilities, so lazy and absent-minded Yoshi just goes with the flow, not really thinking about what happens next.

Until fate accidentally brings him together with Kyouko, a girl who lives in eternal darkness and silence. This will force him to make a hard choice....