Dare I say whatever Gojo x Geto is
The author SPECIFICALLY stated that they're best friends/yin and yang and in symbolism of that in the opening, it shows them as betta fish (betta fish cannot be in the same tank as one another or else they fight to death) stuff like that. Just because two people are CLOSE does NOT mean they like each other romantically. It's like being paired up with yo best friend or something