The culprit in the “throwing things at Mizuki” mystery turns out not to be Rei/Purple, but Sekiya, a third-year who asked class rep Watase Nanako out. She never outright rejected him but said she needed time to think about it, and in the meantime, Sekiya has been stalking her, while taking his frustrations out on Mizuki.
In a meeting Nakamura/Black’s house, the club determines that the best way to get Sekiya off Watase’s back is to make it appear she has a boyfriend, even if it’s a fake one for that purpose. While “pretty boy” Tomoki/Yellow is the most obvious choice, Watase picks a wild card in Nakamura, judging him the best guy to get the job done.
She doesn’t get Nakamura Kazuhiro, but
Hououin Kyouma Ryushouin Touga, his chuuni alter-ego. This proves highly effective at the mall where Watase tells Sekiya she’s already dating someone. As Sekiya follows them while they go clothes shopping (Kaz gets soaked in the rain during his introduction), the stalker is constantly kept off balance by all of the chuuni jargon and Watase’s apparent fondness for it (and knack for translating).
By the time Touga whips out his “Lost Child Apocalypse” tome (at which which the others got a sneak peak while doing a room search) Sekiya is in full chuunibabble overload.
With the stalker dispatched, Watase expresses her gratitude to Nakamura for helping her out, along with Mizuki for giving her courage to deal with Sekiya face-on. For this, Watase asks if she and Mizuki can be friends, and if she’ll call her by her given name, Nanako. Thus the Hero Club completed two missions: ridding Watase of a pest, and getting Mizuki a new friend.
As for Rei/Purple, there’s still something shifty about him, like he’s hovering over all, controlling things. Mizuki’s suspicions were only intensified when he saw Rei with Sekiya outside the mall bathroom, discussing something. We’ll see if there’s anything to this, or if like last week, attention on Rei is directed to someone else. The preview indicates the latter.