Although they're classmates, the two rarely interact in canon. However, they still share a fair amount of interactions with each other. Those interactions are usually used to show Teruteru's "open tastes" when it comes to his sexuality, confirming he's either bisexual or pansexual.
In the Prologue of Super Danganronpa 2: Goodbye Despair, the boys are among those who have fun in the sea. When Teruteru asks the group if anyone would like a rub down of his suntan lotion, Nekomaru actually accepts the offer, not realizing Teruteru's perverted intention. Although the Ultimate Cook's words imply that he was hoping a girl would accept, he's quickly fine with a muscular man accepting instead, saying that "his tastes are pretty open," to which Mahiru replies they may be too open.
Nekomaru is among those who reacted the most sympathetically towards Teruteru upon hearing his motive to kill during the conclusion of Chapter 1's case.
In the first episode of Despair Arc, Teruteru is tied up after making sexual comments towards Sonia Nevermind. Initially, it's his teacher, Chisa Yukizome, who has him tied up. However, because he soon enjoys being tied up by a woman in an apron, Nekomaru quickly replaces her. While Teruteru is briefly confused, he soon ends up enjoying being tied up by a muscular man as well, making this the second time in the franchise that Teruteru was fine with Nekomaru going with his perverted fantasies instead of one of the girls.
- Teruteru – “Heeeey, I got some suntan lotion from the supermarket. Would anyone like a rub down?”
- Nekomaru – “Oh! You're quite considerate! Now then, will you apply it right away?”
- Teruteru – “Eh? Rubbing lotion on a muscular man...? All right, no problem! My tastes are pretty open, you know!”
- — Teruteru offering a rub down of a suntan lotion, which Nekomaru accepts.
- Teruteru – “Mmhmhm... I'll make sure to slather you with lots and lots of oil!”
- Nekomaru – “Wh-What is this feeling of intense bloodlust!?”
- — Nekomaru's reaction to Teruteru's perverted remark.
- Nekomaru – “WHYYYYYYYY!?!? WHY DID YOU KILL HIM!?!?”
- Teruteru – “I-It was a mistake... I'm telling you it was just a mistake... I...was only trying to save you guys... I was only trying to save Nagito from murdering one of you!”
- — Teruteru says why he killed after Nekomaru demands an answer.
- Teruteru – “I-I still don't believe it! There's no way I can believe it... It...it has to be a lie... That's why I wanted to go home! I wanted to...go home and confirm it... I wanted to make sure...it was all just a lie... I wanted to make sure I still have a place to call home!”
- Nekomaru – “Gh...! Teruteru...you...!”
- — Nekomaru reacting with sympathy upon hearing Teruteru's explanation of his motive to kill.
- Nekomaru – “Hey!”
- Teruteru – “Ah! It's a man now? Oh! I can work with this!”
- — Teruteru enjoying being tied up by Nekomaru, in the subbed version of Despair Arc's episode 1.
The ship sailed as a result of Teruteru being more than fine with Nekomaru fulfilling his perverted fantasies instead of one of the girls on two occasions.
While Teruteru's ships tend to be unpopular due to his perverted personality and the character himself being rather unpopular, this ship is one of the most popular ones involving him. Mostly because this ship is often used to show that Teruteru (and imply so with Nekomaru) is a part of LGBT community. Nonetheless, it naturally loses in popularity to Nekomaru's heavily teased ship with Akane. The ship is still a minor one and as such doesn't get many fan fictions or fan arts dedicated to it. It is, however, the second most written ship for Teruteru on Archive of Our Own, losing only to his ship with the protagonist.