Their first interaction is Ryder mistaking him for Colt and treating him like shit while also going 'btw how did u change out of ur costume so fast??' But not actually giving Grace the time to answer and explain that he is not Colt

He, very soon after, runs into the real Colt who explains that he brought his twin on set today and suddenly things make a lot more sense

I lovingly call academia Grace 'crashout Grace', so at this point in time, he's REALLY not into Ryder's bullshit, and eventually has a whole argument with him in front of EVERYBODY. Colt (begrudgingly) pulls Grace aside before an actual fight breaks out, and Ryder tells everyone to keep it moving and gets pissy when someone calls attention to the confrontation.

Little do they know, he has never been more turned on IN HIS LIFE

So now Ryder's actively pursuing Grace bc 1. He needs dat and 2. It pisses Colt off to no end

Eventually, Grace does warm up to Ryder, but he's so blatantly not attracted to him for like the first year of them knowing each other. Grace only starts to fall once Ryder becomes a bit more vulnerable with him. He's still a dick, don't get me wrong, but he reveals more about himself to Grace than he probably has to anyone, bar maybe Gail

They date for about a year before Ryder royally fucks it up somehow and Grace breaks up with him

‘Y'know I really thought there was something different about you, something no one else could see. I was so wrong'

Ryder never really gets over Grace, but he'll tell you that he did

Anyways, fast forward a few years and Grace is back on set again cause they're filming closer to him. This is the point in time where he's been kicked out of academia and became a middle school teacher instead.

He runs into Ryder and they have their first conversation in years and it is soooo awkward, especially cause Ryder's pretending to not gaf while very much gaffing. It goes about as well as it can until a super buff dude with long hair and one arm wraps said arm around Grace's waist. Ryder obviously asks 'who tf is this??' And when Grace is like 'oh! Um, this is Simon! My uh- my boyfriend-' Ryder turns on his heel and leaves SEETHING.