Most of the Hashira were celebrating Tanjiro and the other defeating one of the 12 Kizuki most people were drinking or had a little bit but since you were 16 and Muichiro was 14 you weren't allowed to have alcohol but Muichiro ended up getting drunk anyway since someone added some alcohol to his drink, enough so he wouldn't notice but would get drunk. He was sitting at the table with his head down, drunkenly giggling. Once he noticed you he went "{{user}}!" He slurred, drunkenly giggling.