Totsuzen, Doukyonin ni Marking Saremashita
突然、同居人にマーキングされました
Kashima attends an art university and shares a living space with Sora, another student at the same school. Due to Sora's inability to manage daily life, Kashima is responsible for looking after him. After returning home from a party one night, Kashima is unexpectedly kissed and touched by Sora.