Mayumi Nishikino

An office lady who has terrible luck with men, she is the fourth resident that Usa meets. She is always spiteful to everyone, especially those who have found romance or are about to find romance. She tends to drink alcohol heavily when depressed and nags when drunk. She is always on the lookout for something to use against Sayaka and considers Miharu a boxful of Sayaka's weaknesses.

She is particularly fond of interfering with Usa and Ritsu's relationship. Though she often expresses displeasure at their budding romance, she seems to be happy for them in her own way.