Nagisa Kiryu/Relationships

Mizuki Sera
Nagisa originally disliked how energetic Mizuki is, as well as how her brother is Kaito Sera, but over-time he is seen growing attached to her. This is especially shown in the School Fair Arc and Field Trip Arc. This eventually leads to romantic feelings that are returned, though Mizuki's brother doesn't exactly approve. They share a kiss after Nagisa breaks down in Episode 11.

Iris Shirasaki
Nagisa swore to protect her in his past. He was shown to have romantic feelings for her, but it is revealed to be him trying to figure out how much of her past that she remembers. In the end, she is shown to have romantic feeling for him, but it is not clear if they are returned but seems like he is ready to accept her.

Kaito Sera
Originally, Nagisa acted really hostile toward Kaito. When Kaito told Nagisa that he would protect A-TEC, he replied that Kaito won't be able to defend it, at least until he became CEO. Kaito and Nagisa doesn't use honorifics with each other because Kaito told him that people use honorifics with their elder. Ultimately they decided to stand on a no-respect ground. Later they became good friends.