The reason Todoroki is always in a Tranquil Fury at Deku is because Todoroki is projecting and falsely equating Human Fusion to Quirk Marriages
- It's well known in canon that pretty much all of Todoroki's issues come down to his parents in one way or another. Given how much his dad is a Berserk Button for Todoroki early on and his own loathing of Quirk Marriages - not to mention that Shoto was produced deliberately to have the perfect combination of his parents' quirks - the fact that Izuku's Human Fusion essentially lets him do the same thing by combining and/or upgrading the Quirks of the Fusion Components basically rings all of Todoroki's worst warning bells.
- As evidence, when the students are riding the bus to the USJ the discussion turns to Fusion. After the revelation that Izuku has now also Fused with Mina once, Todoroki deliberately looks over all the girls in class 1-A that Izuku's Fused with before glaring at Izuku, not even seeming to consider that Izuku's also Fused with Bakugou.
- Chapter 14 further supports this belief as he only specifically mentions Ochako and Momo, but not Bakugou.
Following the above, the way Izuku and Todoroki finally become friends will be by Fusing and each getting a look at the other's perspective.
- It's been implied but not stated anywhere that Deku can't fuse with someone against their will, but this hasn't actually been tested. At some point - if the fic mirrors The Stations of the Canon, then probably during the Sports Festival - Izuku will accidentally Fuse with Todoroki and the Mental Fusion aspect will be how the two realize that there's been a misunderstanding... and how Deku finds out about Todoroki's childhood.
Izuku is going to Fuse with a Villain at some point, and it will be Played for Drama
- Given that in addition to Dragon Ball Z, Steven Universe is one of the big inspirations for how Izuku's Human Fusion works, there's a great deal of potential for some terrifying Body Horror by forcing Fusions or unwilling Fusions (whether the power activation is accidental or something else) á la the Cluster.
At some point, Izuku will Fuse with Toga Himiko.
- Seriously. Think about it. All she needs is to successfully pass herself off as someone long enough and Izuku could easily step into it willingly and entirely unaware that it's actually Toga.
- Their Quirk Mutation of Toga's Shapeshifting and Power Copying will result in the ability to turn into any Fusion that Deku has been before. Unfortunately, they will still be as crazy as Toga.
- Flashbang: Can firelight from all parts of his body.
- Ranged Blasts via producing hot or heat-absorbing plasma; or on the ice side, through varying sizes of icicles.
- Something related to her secretions causes Tsuzuru's quirk was?
- Confirmed. Tsuku has enhanced secretions which render a person's body numb within seconds of being hit by her tongue.
- Better radiator.
- Engines on arms and legs.
- Recipro + Full Cowl: improved Super Speed, which could hit supersonic levels.
- Unbreakable state in base.
- Can absorb more metal into themselves, the more they take in, the harder they get.
- Steel version of Unbreakable.
- Two Tails á la Tails.
- More control overvoltage.
- Higher limit before going stupid.
- Turning other objects invisible via touch.
- Sprouting body parts from anywhere on his body.
- Sizeshifter for her whole body.
- Ambipom, as in two tails with hands.
- Dark Shadow that can make more of itself.
- Ranged Blasts + Explosive Touch—> Raging Smash or Freeze Smash Blast, depending on the side Todoroki uses.
- Improved homeostasis, which would potentially resolve Katzuku's Logical Weakness of sweating.
- Sprouting body parts and tails from anywhere on the body.
Izuku will become the center of affection for multiple girls
- Just think, whenever Izuku fuses with someone they become Fire-Forged Friends and gain some of his personality traits. It's totally likely that, eventually, at least ONE of the girls he fuses with will develop feelings for him. As such he'll likely end up in either a Love Triangle or an Unwanted Harem.
- In fact, while the author hasn't decided about including shipping at all in the story, a polyamory has been even considered as an option. It makes sense for some of the boys to be involved as well, especially if more triple fusions happen in the future. Could Mineta develop sincere feelings for Tsuyu, or Katsuki for Ochako? Could Katsuki's apparent jealousy for losing the status of Deku's Only Friend and fusion partner be something more, or could a Kiribaku happen after a triple fusion with Kirishima? However, the characters could be also dubious whether their respective feelings were genuine or just caused by the fusions. The polyamory may not be treated seriously by themselves, just an acknowledgement of the strong bonds that have bene formed between them while waiting to sort their feelings.