Matashige and Akugorou have found that their younger brother, Kosanta, has gone missing and have asked the nearest Oni, the player, to find where their brother is. He left a note saying the he has been kidnapped by Oni-basami and taken to Hosuseri Shrine.
You race over to the shrine and battle your way through the youkai standing in your way and Oni-basami in the final room. When you reach Kosanta, instead of thanking you for saving you he condescends you and asks why you beat up his friend Oni-basami. Stupefied, you tell him that his brothers are worried for him and that he should return to them immediately. Kosanta doesn't see what the big deal was as he says he left a note stating that he would be playing with Oni-basami for the day. He agrees that he needs to return to his brothers, but wants to treat Osa-basami's wounds before he heads back.
When you return to the older brothers they begin the discussion of the letter he left. Kosanta says that the letter he left said he was just playing with Osa-basami, but the physical letter that the two brothers show says directly that he has been kidnapped and for them to send help. Kosanta understands the mistake by saying that he accidentally wrote "Help! I have been kidnapped!" instead of "I am going to play with my friend."