Amashinnaga

Amashinnaga is the poly ship between Rantaro Amami, Korekiyo Shinguji, and Angie Yonaga in the Danganronpa fandom.

Canon
The three don't share many interactions, especially not as a group. This is due to Rantaro's early death as the first victim. However, Korekiyo and Angie happen to share few canon interactions.

Amanaga
There are some parallels between Angie and Rantaro's personalities. Both are able to stay calm while everyone else may be stressed, and can take control of a situation, both in their own ways. The two also have somewhat similar talents; Angie is an artist while Rantaro is an adventurer. Both are talents that are often solitary activities. Both can also be thought of in a spiritual sense, and as good activities for self-discovery. In Chapter 3, Angie makes effigies of the dead students, Rantaro included. One more reason why it sailed was Angie's likes on her profile, that being avacados. The fandom has a joke in which they call Rantaro an avacado, so this easily helped.

Shinnaga
Angie didn't invite Korekiyo to her Student Council. It can be assumed she was aware that Korekiyo, as an anthropologist, knows how cults are started; or that she believed Korekiyo wouldn't give up his desire to leave the academy easily.

Korekiyo was among the students who understood that Angie's Student Council was based on brainwashing, and had no interest in joining them regardless as he stated he does not believe in gods. Nevertheless, Korekiyo considered Angie an admirable friend for his sister and murdered her after she witnessed his other murder plans. During the trial, when he was suspected and began to panic, he appeared annoyed and asked how long they're going to bring that up after Himiko once again mentioned Atua.

During the non-canonical bonus mode Ultimate Talent Development Plan, Angie had a very unusual reaction after Korekiyo stated that he is interested in Atua solely from critical and anthropological point of view. Angie then told him that Atua's business hours are closed for the day, clearly not wishing to have a follower who isn't actually religious. However, Angie then returned to her usual passive aggressive cheerfulness and reminded Korekiyo that he should pray in order to not face judgement.

Amaguji
During Chapter 1, Rantaro had a good impression of Korekiyo and considers him interesting, appearing to be the only one who has a positive view on Korekiyo. The two have very little interaction in the canon main plot, with the only one being when Korekiyo asks Rantaro how he wants to accomplish ending the killing game. However, they have more interactions in the bonus content.

During his first Free Time Event with Kaede, if the player chooses to talk about Kiyo, Rantaro tells Kaede that Korekiyo has a strong personality, but if she takes the time to speak with him she'll understand him. In addition, he emphasizes that Korekiyo is a calm person who seems to be a clever type.

The two also have two events together in the game’s bonus mode, Ultimate Talent Development Plan. In these events, they bond over both of them traveling a lot, their knowledge about various cultures and having sisters who are important to them, seemingly seeing each other briefly whenever they're both in the school area and tell each other where they've been 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", meaning murdering them.

In Danganronpa S: Ultimate Summer Camp, when playing as Korekiyo, you can speak to someone “well-traveled”, which is Rantaro. The interaction starts off by with Korekiyo asking Rantaro for some advice with traveling. Rantaro responds by simply telling Korekiyo to respect the local people’s customs, and try to get along with them. He also adds that he’s sure Korekiyo will be fine. Korekiyo finds this rather reassuring, and goes on about how he’s a beginner at international traveling, despite being out of the borders, which leads to Rantaro offering to be his guide for his first trip. Korekiyo is surprised at first, but soon says he is grateful for this.

In the Danganronpa V3 Relationship Charts, Rantaro comments that he finds Korekiyo really interesting, while Korekiyo just laughs.

Fanon
The ship is considered more of a rare pair in the fandom, most likely because of Shinnaga being included. Though, another probably being because none of these characters are popular at all.