
Anyone noticed He Tian pinching Mo's nipple but he let it happen and pass like it's no big deal? Our lLittle Mo's starting to let He Tian do whatever now~

But if it is the arm, it's still kinda cute, aye? Like, affectionately pinching your fave person's fleshy arm after coming back from whatever your business. A gesture saying, "Hey, I'm back~ Did you miss me?"
After affectionate pinching, the next step or level would be gripping the back of the neck before sliding the arm over the person's shoulder as a greeting.

About http://www.mangago.zone/read-manga/someone_else_s_bl_manhwa/mdx/d_chapter-61/3/
Are you serious Seunghee?? XD
It's because you tried to greet whom you thought was Suhyeok that you ended up bumping into Inbeom, remember! And you know how you've, like, NEVER greeted your classmates first before, remember?? Because you don't wanna be close to anyone or be friends with anyone? So why did you approach "Suhyeok" (whom, again, was not Suhyeok but was Inbeom instead) this morning if you didn't feel a tiny bit comfortable with him, or familiar, or friendly, or 'close' to him? Even if it was mostly because you were excited to know/see if he wore the uniform you lent him. WHICH! Btw, prompts another inquisition: why were you looking forward to him wearing your uniform? Why did it matter so much that you'd get upset about it? And be giddy (don't deny it) about it?
Come on, Seunghee!! Sweet romance is just right around the corner! Specifically in your classroom!
Anyway, the fujoshis know the answers to these questions already but I'd just like to throw the obvious to the oblivious protagonist.
"Are you crazy?!" HE SAYS. O H M Y G O D AS IF YOU'RE THE SANE ONE DISGUSTING SCUM