What if this is just one person imitating Yukari and Yuyuko kissing by using both spare shoes and skirts. Wearing Yukari's shoes and skirt and wearing Yuyuko's shoes in someone's hand and skirt in someone's arms
^^^ Wasn't there a dialogue choice in one of the relationship stories where the mc told one of the maid students that they could address the mc as a big brother or an older sister?
I think yuri is still feasible in BA. imo at least.