Rantaro Amami/Relationships

His sisters
Rantaro felt responsible for his little sisters and wanted to help them and take care of them, to the point that he apparently learned a lot about make-up and other things that are often considered feminine; he claimed that he frequently helped his sisters with nail art. He was especially close with his youngest sister, who always followed him around. After the loss of his sisters, Rantaro blamed himself and set out to search for them by traveling around the world.

In the Ultimate Talent Development plan, it was mentioned that Rantaro's family also had a kind maid when he was a child, who took care of the children and was like another mother for them, and, to him, she seemed like an amazing woman who could do anything. The siblings sometimes had disagreements over silly things like who got to read a picture book first with the maid.

Kaede Akamatsu
Rantaro admires Kaede's ability bring out the best in people, and is impressed by her leadership skills and the way in which she manages to unite the Ultimates after the shock of the Killing Game announcement, even if the unity is only short-lived. As a result of this, however, he does also worry about her attempting to take everyone's troubles into her own hands, and he tells her to take it easy. He cares about Kaede, feeling that she's easy and nice to talk to, and that he's at ease when he's around her.

In the demo version, Rantaro's carefree nature seems to surprise Kaede, and she's curious as to how he stays so composed and relaxed before the Class Trial, and how he can speak out so calmly against Monokuma. She also seems surprised at his supposed lack of interest in finding out what his talent is, she herself being desperate to find out what it is. Throughout Chapter 1 of the game the two grow close, especially during their free time events, in which Kaede states that she wants to be friends with him no matter what. Despite his inability to remember his talent, and the fact that the majority of the other Ultimates treat him with at least some polite suspicion, Kaede still cares for and respects Rantaro, firmly believing that he's not the mastermind of the Killing Game, just a fellow student who wants to get out of it.

Even though the two are friends, Kaede has a tendency to assume that Rantaro is hitting on her, and that he's a womanizer, although he always denies this, saying he's not that sort of person. When he invites her to have tea with him in one of his free time events, she thinks that he is trying to flirt with her, but he insists that it was only a friendly invitation and he doesn't feel that way about her.

In one of the Chapter 1 cutscenes, much to the annoyance of Tsumugi, Rantaro paints Kaede's nails. When picking the design that would best fit her, he makes sure to take the size and length of her nails into consideration, and she is clearly impressed by his skill as she excitedly shows off her nails to an irritated Tsumugi after he's finished painting them.

When Rantaro's body is discovered in the library, Kaede begins to tremble with fear. She thinks that she's the one who murdered him, as the weapon used to deliver the final blow was the same as the one she'd planned, and he'd been lured into its path but the trick she'd come up with. The trap was originally meant as an attempt to get rid of the mastermind, but instead of doing that she'd actually ended up killing a dear friend. She tells the remaining students that she will figure out who murdered Rantaro, and says that she will never forgive the person who did such a thing. Later, in the trial, she confesses to being the blackened, after attempting to lead the others to this conclusion. Before she's executed, she apologizes to everyone that it's now impossible for all of them to escape the Killing Game together, and apologizes again to Shuichi, her closest friend, and Rantaro, clearly having been torn up by remorse and regret as a result of her actions.

In the non-canon Danganronpa V3 bonus mode Ultimate Talent Development Plan, Kaede is waiting for Rantaro near the end of the Christmas party. Kaede left some cake for him, and, in the end, they ate the leftover cake together. There is also an event where Kaede visits Rantaro at his soccer game to wish him luck and cheer him on.

Shuichi Saihara
When Rantaro meets Kaede and Shuichi, Shuichi seems confused at Rantaro's mention of everyone getting simultaneous amnesia, purposefully, and he seems a little shocked by the idea, despite the fact that it's undeniably a pretty likely theory. He thinks he is in some way mysterious, and knows more than he lets on. Rantaro is shown to have strong faith in Shuichi's abilities and considers him a real detective, even though Shuichi still doubts this himself, but later in Chapter 1, Shuichi begins to grown quite hostile towards him, strongly suspecting that he's the mastermind and that's the reason he "doesn't remember" his talent.

In the Love Suite event, Rantaro has the role of a private tutor or a teacher of Shuichi. As the situation reflects the relationship between Rantaro and his younger siblings, he treats Shuichi like a child, which makes him uncomfortable, and because of this, Rantaro assumes that Shuichi dislikes him, although he denies it. Rantaro seems somewhat relieved by this, although it's clearly on his mind because he soon states that he can no longer be Shuichi's teacher, thinking he made him uneasy, and adding the point that being in contact with him could potentially be dangerous. He wishes to protect Shuichi, so he doesn't lose another person who is important to him. He mentions the possibility of himself dying, and while he claims he's joking, Shuichi seems skeptical. Shuichi tells Rantaro he would rather hear the story about why he could be dangerous, even if it is a risk, rather than leave Rantaro to deal with it alone. At the end of the event, he looks very glad, starting to trust Shuichi and promising that he will one day tell him his story.

During the bonus mode, Love Across the Universe, Rantaro slowly warms up to and explains his situation to Shuichi. He is very glad that Shuichi believes in his goal to find his sisters, since nobody else but him does. He promised to become Rantaro's traveling companion in the search of his sisters, which could even last a lifetime, and Rantaro is moved, finding in himself anew the motivation to become a real Ultimate Big Brother.

Tsumugi Shirogane
Just before the Chapter 1 cutscene, Tsumugi is painting Kaede's nails with the brush she gave her earlier. As soon as she's finished, Rantaro comes into the room, asking what the two of them are up to, and telling them that he can do nails too. He suggests a suitable design for Kaede's nails, and then proceeds to paint over what Tsumugi has just done on them. She can be seen watching this whole ordeal with a disgusted expression on her face, and making unhelpful comments throughout the scene, clearly annoyed at Rantaro.

It was revealed in Chapter 6 that Tsumugi was the one who killed Rantaro, not Kaede. Tsumugi didn't want Rantaro to discover the secret and ruin the fun of the Killing Game, so she used Kaede's plan to kill the mastermind as a means to murder him and frame her, therefore saving herself. Both Kaede and Rantaro were some of the most determined to get out of the school, so she decided that they had to go before they found anything out. This consisted of Tsumugi also being found out as the mastermind.

Korekiyo Shinguji
During Chapter 1, Rantaro has a good impression of Korekiyo and considers him interesting, appearing to be the only one who has a positive view of him.

During his first Free Time Event with Kaede, Rantaro tells her that Korekiyo has a strong personality, but if she takes the time to speak with him she'll begin to understand him. He compliments Korekiyo, saying that he's a calm person who seems to be one of the more clever types.

In the non-canon bonus mode Ultimate Talent Development Plan, it's shown that Rantaro and Korekiyo are very good friends. They share a great interest in traveling and they both have a close relationship with their sisters, seeing each other briefly whenever they're both in the school area and telling each other what they've been up to lately. However, it's also implied that Korekiyo has taken interest in meeting Rantaro's sisters in order to make them his sister's "friends".

K1-B0
While the two aren't seen interacting much, it's shown in one of Rantaro's Free Time Events with Kaede that he does appear to have a bit more respect towards the robot than most of the other students. He recognizes that K1-B0's personality isn't as unique as his status as a robot, but he believes K1-B0 is on their side, considering the Three Laws of Robotics, and while talking with Shuichi, he smiles awkwardly as he says that he probably shouldn't say bad things about robots, because K1-B0 wouldn't like that.

During the Demo version, Rantaro spent a lot of time with K1-B0 and later vouched for his innocence during the beginning of the trial. The two sat out of it due to the lack of space.

Miu Iruma
Rantaro is a bit overwhelmed by Miu's foul mouth, but he doesn't seem to dislike her as much as some other students do.

When Kaede and Rantaro talk about some of their more unique classmates during his Free Time Events, Rantaro mentions that Miu's talent is beyond understanding for ordinary people like them, and he mentions that he understands her thought process, though and that she likes to be the one on top. Kaede gets confused by the wording of this phrase, and Rantaro laughs a little awkwardly, saying that he was just trying to make a joke.