normally obito takes it. If it's 8th gate then it's a point of debate and it all comes down to one thing. Which gives out first? 5 min. Continuous kamui or gai. And if even for a second gai leaves obito in those 5 min. then **** cause he is again back with 5 minutes. Oh well! obito wins this. Give him both eyes and he makes kamui gg reality.
Against 1-7th gate, Obito could troll by acting like Tobi.
Against 8th gate, Gai actually stands a chance, but night moth/guy is suicide against intangibility, and Evening Elephant isn't continuous so it can't hit him for 5 minutes.