When they're little, Bakugou and Izuku make a promise to one another; they'd always be best friends. The next morning, Bakugou's quirk manifests and their worlds change (for better or worse, time could only tell).

When they finally hit middle school, Izuku tells himself that he'll make amends or forget about Bakugou. The next morning, his childhood best friend beats him bloody and Izuku can't quite forget.

When Izuku finally inherits One for All, he thinks Bakugou will see him as an equal. The next morning, his old friend screams at him and tell him he'll always be inferior- always be the same Deku.

Izuku finally tells Bakugou that Deku means not giving up. He next morning, Bakugou feels that familiar Deku-related feeling in his gut grow along with an ounce of respect. He thinks he hates this boy, he thinks emotion that doesn't feed his flames is weakness. He hates the idea of being weak. Conclusion: he must hate Izuku.

The two fight alongside one another in unison, a perfect team against their shared idol, All Might and they win. Bakugou has to admit that Izuku is strong but he says he'll always be on top no matter what and Izuku better remember that.

They graduate together years later- it's a miracle they've come this far. Bakugou has grown used to that ugly mug of Izuku's, has grown used to the bright eyes and unruly green hair and freckles that make him believe in angel kisses. He doesn't want to see Izuku bleed; Deku means never giving up. Izuku knows his Kacchan will never hurt him again, not now that they share a stage graduating as equals. The two haven't butt heads- or rather Bakugou butting his head- since the summer between their first and second year, and frankly neither is eager to start again, unless they're sparring of course. They are finally equals. The next morning, they're real heroes and they're too busy to be faux rivals any longer- at least actively.

They're both in their twenties when they have to team up together to take down a particularly awful villain. Bakugou still hates depending on anyone, even Izuku who he trusts more than anyone, and because of it they almost lose- almost, of course, because Bakugou and Izuku together are unstoppable. The next morning, they're going their separate ways again but not before Izuku asks for Bakugou's phone number in case there's any dire emergency.

The first time Izuku calls Bakugou- after making sure the latter wasn't busy, because he knew even he wasn't safe from Bakugou's wrath- it's because Izuku has just bumped into Tsuyu again and she's doing great work as a frog-hero. The next morning, Bakugou gets a mission and forgets to call Izuku back.

They're almost in their thirties when Izuku is officially pronounced the second Symbol of Peace. No one knows about One for All, except Bakugou who had never once believed or given a second thought to Izuku's confession at the very beginning of their freshman year as Heroes-in-Training. As such, Bakugou is listed as second or arguably third strongest hero out there depending on who you asked, some people brought his name below Todoroki's because of his attitude but Bakugou had never given much of a fuck about that. The next morning, he still doesn't pick up when Izuku calls him.

In their mid-thirties, Izuku begins his quest to find another suitor for One for All. He finds a young dark skinned girl without a quirk and a heart bigger than the world and determination to outshine even a young Izuku's and he thinks she's perfect. He calls Bakugou to catch up, feeling more nostalgic than usual, and the latter doesn't pick up- still a bit childish at times for his age, Bakugou will never live this mistake down.

It's on the news that All for One's new wielder is raging war on all heroes; nothing new but still a big problem for heroes everywhere. Bakugou is on the other side of the world burying his mother, he doesn't make it to back Japan in nearly enough time. The next morning, he sees a familiar name on the list of mortally wounded heroes.

Bakugou gets the first flight possible to Japan, torn between blaming the timing of the universe and blaming himself for not being there. When he gets to the hospital, it's a day too late and Izuku's body is cold. He watches his second loved one get put into the ground within a week. He never got to tell the other how he'd felt all those years, thinking he had all the time in the world.

There's odd news of who was in the old Symbol of Peace's will, a small Jamaican-Japanese girl who Bakugou had never heard of and he knows he needs to talk to her right away- he doesn't know why he feels the urge but his legs pump him as fast as they can. She explains to him how Izuku had been her mentor the last 7 years and how she had inherited his will, his power. Bakugou remembers for the first time in twenty-odd years the day Izuku had spilled his guts to him and he'd screamed in anger, accusing the boy of lying. The next morning, he begins training her in his friend's stead.

Bakugou knows all too well Izuku's determination, and he'll see the world burn to hell before his spits on that image by letting his student possess a power she didn't understand and lead a life of pain. It was the least he could do, and he did so for the many years to come.