Hikari's Friendless Background predicament at the start of the series. Throughout junior high as well as high school, he was mocked by his classmates for his otaku lifestyle. Even Arisa of all characters belittled him when they first met until she learned about his mental state.
Iroha's backstory consists of other classmates ridiculing her for her ill temper and seemingly promiscuous nature.
Arisa being taken advantage of by Shun, a boy whom she thought was handsome and charming. She finds out the hard way that breaking up with Shun after Iroha beats the crap out of him causes her to burst into tears.
Mitsuya sets Hikari up as a pedophile in the park. Hikari's Heroic BSoD is understandable considering that the police were involved, everyone save for his family, Ito and Iroha turned their backs on him, and Mitsuya used the opportunity to try and unsuccessfully steal Iroha for himself.
Sumie getting teased and laughed at by her fellow classmates just because she's an anime geek like Hikari.
Hikari and Iroha share a touching moment with each other at the school's roof before she leaves to have her brain surgery. Iroha knows that she will lose some of her memories after the surgery. Iroha makes a promise to Hikari to forget about her. And it goes From Bad to Worse when Iroha has to move away to Los Angeles to start university following her brain surgery and Hikari gets deeply affected by her departure to the point that he didn't go to school for a few days.
A Tears of Joy example occurs when Iroha reunites with Hikari and her friends after most of her memories return.
