Faylicia
The problem with shipping is that, you can want everyone to be happy, but there's always that pairing or character you want happy above all else, so you will end up in their team, so even if you do want to see Seju happy too, your main focus is Sumin and Sungji happiness, so you're always going to be part of Team Blonde because of that.
As for Team Black, well, I say it's about Sumin getting both because Pink is about Seju ending up with her, while Blonde is Sungji ending up with her, but I believe it could go either way, I think it could happen that the three of them end up loving each other if we had more chapters, but if treesome ever happens I think it's more logical that Sumin end up having two girlfriends, so I don't think Seju and Sungji would sleep with each other since they just love Sumin, but I do think they would have threeway sex if she wanted.
dofudofu
Fandom is serious business, especially when it comes to shipping.
sia ue
I think it's already too late to create a team like this, I don't think it is necessary to create a new team because it's pretty much sure Seju will never end up with Sumin again, so it' easier to just change the meaning of the team instead of adding one more and making things more confusing.
Okay, so let's sort out what teams we have:
Team Pink = Those who want Seju happy without ending up with with Sumin
Team Blonde = Sumin x Sungji, or just those who are on the side of one of them
Team Black = Threesome ending
Team Blue = Seju x Nami
Impossible Team Pink = Seju x Sumin
Someone thinks we need any other team? Can we agree those will be the teams now?
I personally think Team Black should be reserved for people who want Sumin to be happy regardless of she is with and Impossible Team Black being used for the threesome ending??