With a story-heavy franchise like Full Metal Panic that focuses heavily on serious military drama, it might be difficult to view a goofy spinoff show like Fumoffu as necessary to the overall canon. After all, there’s nothing in Fumoffu that ever pops up again in any other part of the story. It’s not like Sousuke gloriously rides off into the sunset in Invisible Victory to save Kaname piloting Bonta-kun, or like anyone is going to bring up that strangely problematic rugby team Sousuke trained. That being said, if you’re looking into Full Metal Panic with its recent revival but just want to skip to main story bits… please don’t! Fumoffu is actually key to enjoying the entirety of the franchise. Here’s why!

If you were to just watch the original 2002 anime series, you’d get a gist of how the pair gets along: Sousuke is covert ops in a military organization who was first assigned to protect Kaname, but over time, their relationship grows more intimate. You get a few comedic episodes at the very beginning that set this up but the show slowly becomes more and more dramatic. It ends with a sweet exchange between the two where Sousuke shows Kaname his favorite secret fishing spot.

But only seeing a couple of episodes of this wacky banter doesn’t really do their relationship justice. Everything about Sousuke’s character hinges precisely on what he loses if he loses Kaname: his chance at redemption, his chance of living a free life, and his ability to adapt to a civilian lifestyle. And Fumoffu, for all its insanity, makes Sousuke’s life seem really fun. Yeah, it’s a little silly at times, but you need to really experience what Sousuke is going through in Fumoffu to really appreciate everything he needs to protect.

There’s a fantastic scene in Full Metal Panic: The Second Raid where Wraith is forced to confront Sousuke. Wraith mentions that they’ve been watching Sousuke’s school antics and getting a laugh over how, in spite of what Sousuke believes, he’s been nothing but a burden. When you hear this, you look back on when Sousuke blew up the school’s shoe locker in Fumoffu because a girl invaded his privacy by sticking a love note in his space, or how he literally captured women and threw them into cages for the sake of winning a contest. You can’t help but think Wraith’s got a point.

If you only watched the original anime, all you would think is “Well yeah, duh”. You’d see how Sousuke is a fish-out-of-water who was never destined to get involved with anyone normal. You’d miss out on him connecting with Atsunobu Hayashimizu (the student council president) by inadvertently indulging Hayashimizu in his power fantasies, or developing a not-terribly-friendly rivalry with Issei Tsubaki. He does end up making friends in his own way, and by doing this, it normalizes Sousuke’s actions. They’re just what you think everyone accepts as wacky antics before turning this view on its head later. Trying to fit this all into the same show with the plots of Second Raid or Invisible Victory would make them tonal messes, but regulating them to their own show and dubbing it a spinoff gives it some distance.