Sedoretu was created by Sci Fi author Ursula K. Le Guin and refers to a marriage concept that involves four people: usually a morning man and woman and an evening man and woman. It is taboo for one morning person to be in a non-platonic relationship with the other morning person, but expected for their relationships with the two evening people to be sexual. But for the purposes of this challenge it's fine to just think of it as an OT4 since it's such a short ficlet.

I would also like to thank Pixiv for opening my eyes to this OT4, because wow. And rereading the Seirin First Year flashback made me realise that it was kind of Izuki who brought Hyuuga, Riko and Kiyoshi together, gosh.

This was what they had promised their coach to show the depths of their determination: that they will all make a love confession if Seirin loses. Naked. In front of the whole school.

As time went on, and the First Years got used to life in Seirin's basketball club, they realised something: that the potential sedoretu between the Coach, the Captain, the Centre, and the Point Guard was completely obvious to just about everyone that wasn't the four of them.

"Does that mean they'll be confessing to each other, naked, if we lose?" Was what Fukuda brought up one day, during a break at practice while the First Years were gossiping about the one topic they never get tired of talking about – the utter obliviousness of their sempai when it came to their own love lives.

"Are you guys sure they're not together already? I mean, you Japanese people are so undemonstrative in the first place."

"Please shut up, Kagami-kun. Also, stop talking like you're not Japanese yourself."

"You know, I kind of want to see that," Furihata said, ignoring both the fight developing beside him and Kawahara's shocked "You want to see the sempai naked?" with ease. "I don't mean it in a weird way! Just that it would be kind of funny! You guys can stop looking at me like that you know…Hyuuga-sempai's is standing right behind me, isn't he."

"That's right," said Hyuuga, one hand falling heavily onto Furihata's shoulder. "If you brats have enough free time to natter about the love lives of your sempai, you have more than enough free time for 50 LAPS AROUND THE SCHOOL!"

Broken out of their petrified states, the First Years leapt for the doors, trailing terrified apologies behind them as they ran. All except for one.

"Just one question, Hyuuga-sempai. Between you and Kiyoshi-sempai, which one of you is the Morning wife?"

"Just shut up and run, Kuroko," Hyuuga snapped back, glaring holes into Kuroko's back as he leisurely followed the other First Years.

"Aren't you being a little harsh on them?" Turning around revealed Kiyoshi standing by Hyuuga's shoulder, that familiar smile on his face.

"You heard that, didn't you?" Hyuuga sighed. "This kind of thing needs to be nipped off at the bud. Before it gets any crazier."

"What's wrong with it? I wouldn't mind being in a sedoretu with you guys." Kiyoshi was still smiling that smile.

"I-you- DO YOU HAVE NO SHAME?!"

"Since it's basketball practice, don't you think we should be concentrating on basketball, you guys?"

"Coach, you-"

"Riko, your face is all red!"

"I think you guys should join the First Years in their laps, don't you?" Riko bit out, glaring at the two of them hotly.

Watching Hyuuga and Kiyoshi run off, Riko was uncomfortably aware of the looks the other Second Years were sending her. And the matching heavy blush that Izuki was sporting on the other side of the court.

"I- I wouldn't mind being in a four-man team-up with the three of you!"

Nigou's soft panting was unbearable loud in the resulting silence.

"I'll just go start on my laps, shall I?" Izuki sprinted out the door, face still as red as Riko's. Behind her, she could hear the others' giving in to their prurience.

"Was that supposed to be a pun?"

"It doesn't work very well when basketball is made up of a team of five people, huh."

"YOU GUYS JOIN THEM TOO," said Riko, unable to look at them in the face as they ran past her. Mitobe's hand landed gently on her shoulder as he did so, and Riko couldn't help but let a giddy smile reach her face as she jogged after everyone. It's okay, there's no one watching with her at their backs.