I do not think Shirasaki's personality shifted because he was in love. His personality shifted because :
1) He left the ideal world of college and entered the real world, and found out things didn't work as he expected, he couldn't land jobs as an actor (it's been years), he was serving tables, he was disillusioned, and he lost confidence in his craft and as person (there's something about finishing college and not being able to find a job that is really sad and depressing)
2) When Shirasaki and Hayama where in college, Shirasaki saw him as an equal, that's why he could voice his thoughts, but now he sees him as someone who has accomplished much more than he has, and he therefore feels unworthy.
This was my assessment as well. You eloquently wrote it so I won't add more.
Excited for this one too! I'm hoping it has more continuation or completion after Silhouette of Your Voice, which felt too open or incomplete to me, if I remember it right. But that's what J-dramas do...dang it.
FortPeatForever:
Day 26- Did I step in poo, The worst Ex?
Oh that is easy it is 100% Gun (Sky's ex from LITA). I hate him so much.
Day 26- Did I step in poo, The worst Ex? There are so many to choose from. Today's winner is Uea's ex from Bed Friend. Runner-up is Knock's ex, Plern Pleng, from Together with Me.