It's the time of Walpurgis Nacht again. For those unfamiliar with the celebration, the first of May is the international equivalent of labor day. In Finland it's celebrated as the day of workers and high school graduates by drinking champagne and mead and eating doughnuts and tippaleipä, (Engl. droplet bread) a version of funnel cake. It's also the time with easily the most confetti and balloons around. Traditionally the only celebration in Finland where people are actually joyful instead of being only drunk.
The joke is reminiscent of the parent post on how oni should apparently have two horns. Yuugi finds that hat and pretends to have two horns like a proper oni. Sukia comes around giving Yuugi the stink eye, so Yuugi politely gives Suika her opinion on the matter. On an unrelated note, Suika also goes to visit the Hakurei Shrine shortly thereafter.