The four of them are students in the Ultimate Academy for Gifted Juveniles, they are also participants of the Killing School Semester featured in Danganronpa V3: Killing Harmony. They aren't seen interacting on screen.
Rantaro's interaction with Kaito, Kokichi and Shuichi. Rantaro and Kaito had barely to no interaction with each other, however it is shown that Kaito did see him as a friend, this is more clearly shown after Rantaro's death.
Same as Rantaro and Kaito, he and Kokichi also have barely interacted with each other. It is known that Rantaro can be a bit annoyed with Kokichi's behaviour sometimes.
There is more interaction between Rantaro and Shuichi. When Rantaro first met Shuichi and Kaede, Shuichi was confused on how he mentioned about everyone gathering and getting amnesia at the same time. It's also known that Rantaro is shown to have a strong faith in Shuichi and his abilities and considered him a real detective, even though Shuichi still doubts himself.
Kokichi's interaction with Kaito, Rantaro and Shuichi. Kokichi and Rantaro did not interact with each other much. However we do see Kokichi crying after he saw Rantaro's corpse this was not for long though since his attitude changed rather quickly after that. Later on we can see that Kokichi has the life-like statue of Rantaro, made by Angie Yonaga, hanging upside down next to his bed. This indicates that Kokichi had more interest in Rantaro rather than in Keade, Kirumi or Ryoma. We also know that Kokichi called him "My dearest Rantaro" and in the original Japanese version "My beloved Amami-chan".
Kaito's interaction with Kokichi, Rantaro and Shuichi. Kaito and Rantaro have not interacted with each other much, however he did see Rantaro as a friend, this is more clearly shown after they all gathered in the library because of the body discovery announcement. When Kaito saw Rantaro was dead. He was angered at the loss of his friend, he even went so far as to ask all them who did it and he would “punch them into orbit”.
Shuichi's interaction with Kaito, Kokichi and Rantaro. There is some interaction between Shuichi and Rantaro. When Shuichi and Kaede First met Rantaro, he was confused at Rantaro's mention of everyone getting amnesia at the same time and Shuichi did seem a little shocked with that idea, but despite this the fact that it's undeniably a pretty likely theory. We do also know that he thinks that Rantaro is mysterious in some way, and that he knows more about it than he tells. However, later in chapter 1, Shuichi began to strongly suspect Rantaro of being the mastermind and that thus the reason being why he can't remember his Ultimate talent and that's why Shuichi grows quite hostile towards him. It's also seen that Rantaro believes in Shuichi's abilities and Shuichi himself. Rantaro did also consider him a real detective, despite Shuichi not believing in himself.
The ship mostly sailed because all the characters in this ship are the most popular male characters, and they are often shipped among themselves. The most popular ship among them is Saiouma. People did also start to like the dynamic between them, and since they are some of the popular characters present in V3, They gained quite some shippers.
- Amasai refers to the ship between Shuichi and Rantaro
- Kaimami refers to the ship between Kaito and Rantaro
- Oumamasai refers to the ship between Kokichi, Rantaro and Shuichi
- Oumami refers to the ship between Kokichi and Rantaro
- Oumota refers to the ship between Kaito and Kokichi
- Saimota refers to the ship between Kaito and Shuichi
- Saiouma refers to the ship between Kokichi and Shuichi
- Saioumota refers to the ship between Kaito, Kokichi and Shuichi