Oisuke is a yōkai who briefly appears in the series.
Oisuke is a yōkai who resembles an oyster. His body color is a gradient of blue and green.
Oisuke first appears in Chapter 44, when he asks Haruitsuki to exorcise him. But before he was going to be exorcised, he asks if he can get his home. Haruitsuki and Hanae agree and they went to the park where Oisuke said his home was beneath a watermelon. When Hanae tries to pick it up, two kids show up and said that they are going to break the watermelon and gets angry at Hanae for trying to move it. They get scared as they assume Haruitsuki as a gang leader and Hanae as his henchman. They said that they are going to break it in ten seconds. One of the kids starts running towards the watermelon. Oisuke, realizing that they intend to hit the watermelon with a stick, runs out in the kid’s path shouting that his home will be destroyed. Haruitsuki steps in to protect Oisuke, but Hanae shouts to stop as he was afraid that Haruitsuki might get injured. He holds Haruitsuki back and kicks the stick away.
After that, the kids stop and Hanae starts to digging to find Oisuke's home. After he finds it, Abeno then exorcises him.