Shadow knows two things.
One, he's very bad with emotions
Two, he's very much head over heels for his best friend but he'd never tell you
Stag also knows two things.
One, there's a server shipping him and Shadow.
Two, Shadow is being weird and he doesn't know what to do.
Shadow has dedicated his life to being better and stronger than Sonic after becoming acquainted with the hero. He tries desperately to keep Sonic under his thumb, but somehow Sonic has always gotten on his good side. No matter how much Shadow wants to move on, there's always something in the back of his mind. And that something may cause him to lose the only other person he cares about.