The Brother's Worries About His Sister Worry His Friend

Summary
Agata's concerns over his sister's love life and the supposed complications therein have been taking up all of his thoughts, causing him to act strangely and score poorly on exams. This in turn worries Michiru, who decides to do something to resolve the issue. After talking to Saaya, Michiru realizes that she has a crush on Bossun and not Tsubaki, contrary to what Agata believes. The following Saturday, he visits the Agata household under the premise of studying with Agata, when in reality he intends to correct the latter's mistaken conclusion about Saaya's love life. After a harrowing day, Michiru leaves with the belief that he has changed Agata's mindset. That night, as Agata settles in to go to sleep, he suddenly has a new mistaken realization: that Michiru and Saaya are the ones who are mutually in love.