I do love the evil Suns AUs, I truly do, but I do think canonical Seven Red Suns deserves love too.
Five Pebbles is a mentally unstable iterator and has been for a long time, this is established multiple times. Suns became his mentor because they wanted to make progress on this sort of mentality, and defends him when Sig points it out, mentioning how they were helping him get better.
Suns is so deeply caring, and the reason they even became Pebbles' mentor was to try to help him, try to coax him out of his shell and assist him in refining his theories. They're research partners and friends, because Suns saw someone in need of just that, and knew they could help.
And, it's very likely Suns doesn't even realize how badly the "bug in a maze" comment hurt him, as it's common for friends to say something and for it to accidentally hurt when they meant it to help, and Pebbles is already a defensive iterator who wouldn't confide that "this comment hurt me". They just had no means of knowing how much it hurt him, up until he lashed out at perceived pity when all they wanted was to gently calm him down.
They also saw he was miserable, and honestly was making no progress (Sig cites that he's plateaued at his angsty phase) and then, and only then, offers what they hope would help make their beloved friend happy. They include specific instructions on how to perform the experiment safely and slowly, and the main reason it fails is because, not due to Moon's interruption, not due to faulty information, but because Pebbles rushed into it far too fast.
And Suns laments about how they shouldn't have given their, again, very mentally unstable iterator friend the plans, because hindsight is perfect and they only then realized how he would have rushed it and hurt himself, and Moon, in the process.
Plus, they adore their weird purple dog, getting attached when they knew they shouldn't, making a messenger they know can return.
Seven Red Suns is a character defined by caring too much in an uncaring world, wanting their friends to be happy and sheer misfortune following them. They are a tragedy because of their love, and that's something fascinating.
And also they've got these vibes.
