My favorite things to think up is habits, like the small things people would do without fully recognizing it themself. So, in that, here is some habits that Suguru would have toward people he cares for:
-> When he's holding something a mug, phone, book, or even the hand of someone's, Suguru absentmindedly rubs little circles with his thumb. Usually it's for no apprant reason, usually when he is thinking. At times, however, it's completely on purpose, but more so a way he half comforts himself.
-> When a hint stressed of overwhelmed, he runs his fingers from forehead to crown even when not a hair is out of place.
-> Instead of laughing right away, Suguru lets out a quiet hum or puff of air through his nose, corners of his mouth curling before the actual laugh comes spilling out.
-> When entering a room or area, unlike Satoru who tends to scan the space as a whole, Suguru's eyes finds faces first before going elsewhere. An instinct of his to read moods before interacting with the people or place.
-> When Satoru, or you are speaking to him, Suguru ever so slightly leans toward the other person. Not his full weight, but an ever so subtle tilt, a way you can tell his attention, even if his eyes are elsewhere, is fully on who is speaking. If you and Satoru are speaking, he tends to always look as well, before Satoru to you and back again.
-> Kinda a random one that came to mind, but Suguru is so the type to organize parts of rooms when on a phone call. He's in the kitchen? The counters get wiped. He's in Satoru's room? Satoru's whole desk gets straightened out. He just needs to do something small, not because he is thinking about chores, just more just the need to keep his hands occupied.
Yepppp that's all for now. :]