We Outside!!!

A) they never saw how he lives

B) they are the only 2 that can talk to Sakura in a non hand holding way and by that I mean Sugimomo (momosugi) keep it realer than real in their prev deep conversations with him in ways sometimes closer pals like Sakura's usual crew couldn't do (thanks Nii sensei with the foreshadowing of that w/ Togame chatting up Sakura at the festival)

And it was a reminder that he shouldn't have went so hard for Nirei who caused the issue in the 1st place (glad Nirei learned his lesson tho and started training) when Nirei usually stays behind Suo

Suo tried to hurt Nirei emotionally and physically so Nirei could accept his excuses for ghosting the rest of Furin and Nirei was the one who actually became a handful for Suo (reading Suo's expressions + conflicted words/actions like a book). Nirei proved to us he is quite mentally fortified and he can hold his own even if it's a losing battle for him. Funny since Suo once deemed fighting Sakura would be a hassle hence why he never officially accepted Sakura's issued challenge.

Then we have Sakura who isn't used to this level of abandonment. People have openly told him they didn't want him around (his father) so he always knew where he stood with people, but here comes Suo breaking down the walls, getting close, becoming some he can fight alongside with back to back taking on foes together. And to top it off, Suo doesn't even have the guts to properly say goodbye to him - only to Nirei. That's heartbreaking. Suo may not have fought Sakura but he emotionally hurt him all bc Suo thought he was doing what's best (cuz remember they all only 15 so they're not taking this well, the Furin trio all miserable)

And I know I've seen some comments (not on tumblr) where people are thinking Nirei got sidelined for how close Suosaku are but imho Sakura's reaction is highlighted more bc we know that Sakura is used to having no one in his corner and now to have lost Suo in this way is deeply triggering for a lonely neglected child like Sakura. Secondly Nirei accepted somethings up with Suo, he is the sole witness to Suo's body language and expressions, and he doesn't seem as angry but moreso confused as to why Suo did them like this. Sakura is dealing with his former vice captain Suo resigning out of the blue after assuming Suo would eventually pop back up to hang with them like normal. Nirei already suspected Suo was being weird pre Suo leavin so he had more time to process Suo's decision.

We learn that Sakura and Kiryu got homelife/family issues (particularly daddy issues). Suo's home life is also complicated as Red Chanpuru member. We learn Nirei wants to become stronger at fighting after being bullied. Suo is all for it. But then we have Tsuguera who is, so far, just a guy.

Suo takes on the responsibility as older brother figure to the kids, he's listening to adults' problems and fixing the situations they land themselves in like the reliable good natured child he is, he uses multiple languages to translate (very much like children of immigrant parents having to handle conversations b/n 2 adults or more that can't understand each other)

Suo's snippet as a Red Chanpuru member also highlights his skills/traits that explain Furin Suo's actions in past chapters. From training Nirei ➡ us reading the kids training, to settling adults arguing ➡ Sakura and Sugishita shaking hands instead of fighting on the 1st day of school as per Suo's suggestion, to the child with the sick mother giving me flashbacks to Momijikawa's sick grandma and the hungry kids reminding me of when Suo and gang fought against the Gravel team in the red-light district who had to split a cookie among several members cuz resources weren't available in their town