Coming from the absolutely unexpected confession last episode this feels.. weird. I expected some form of friction to still be there but no it seems like both of their wants and desires line up quite well but on the other hand this outcome makes much more sense given how both of them have been portrayed so far. Marin doesn't even have a cosplay account so her prioritizing cosplay itself over the attention it gets her is nothing new really. Whereas with Gojo we're well past the point of knowing Hina dolls are no longer priority #1 in his life.
For all I care this can devolve into nothing more than diabetes inducing fluff without any of the supporting cast but I think we still have some more regular plot available with the semi-ongoing references to the "Mandate of Heaven" author positively reacting to Marin's cosplay of Haniel. Gut feeling say they'll do one final cosplay as a couple going completely all out and then we'll get a nice happy end. I'll be happy to be proven wrong if even more plot to follows though.