Who does Fin actually go out with? PB 火災, 火 Princess?

this should be a クイズ question... it's FP, flame princess.

Okay, Princess Bubblegum was Finn's first 愛 interest, but they never dated. It may have seemed like they did, but they didn't. That's a fact. Pincess Bubblegum just returned Finn's affection in her own ways, but they were never official. Period.
Flame Princess, on the other hand, was Finn's first and true girlfriend. As seen in episodes such as "Burning Low" and "Vault of Bones". He also stated in "Puhoy", when he was dancing with Roselinen, that he had a girlfriend, which was Flame Princess. But, in "Frost & Fire" (saddest and most shocking episode, ever.), they broke up because Finn did used personal things against Flame Princess, in which Finn was one of the only people she considered trustworthy. Finn then tried to give PB a shot again ("Too Old"), but she turned him down. He tried FP in "Earth & Water", but Flame Princess became the ruler of the 火災, 火 Kingdom, and so Finn and FP were still over, but FP still cared for Finn as a friend.
In Flame Princess's latest appearance, "The Red Throne", Don Jon and Flame King take over the 火災, 火 kingdom, and Flame Princess and Cinnamon Bun go to Finn for help. But in the end, Cinnamon Bun takes place as Flame Princess's knight, saying that he loves her.

Finn used to go out with Flame Princess but now they have broken up.It will actually seem that Finn goes out with flame princess as she is the only one that truly loved him while they were dating.
If あなた see everything differently, maybe it may be possible that PB likes Finn. She kind of showed affection to him in "Too Young". But after she turned back to 18(biological age), she changed and does not feel the same way again. It may have something to do with the age gap または maybe she just returned Finn's affection in her own ways just like what emerald_32 said. Besides, PB and Finn were never even official yet.

FP and finn all the way!

i THINK 火災, 火 princess because princess bubblegum talks about how she is to old for finn and that she has people to take care of (the キャンディー people).also, finn and the 火災, 火 princess like each other so i think they probably dated... right?

Princess Bubblegum was his 愛 interest not anything huge, because she rejected him many times to the point of making him cry and holding a picture of her in "Icendium." Flame Princess on the other hand is the true girlfriend for Finn its really undeniable to turn down Finname when its so adorable. In "Burning Low" Finn saved FP によって giving her oxygen and 火災, 火 can't make flames without oxygen and that's pretty legit right there. But currently Finname is in a rough place.