Yuri was the only one concerned (low key freaking out) when Yuko fell in a puddle of her fangirl blood. (Yuuri’s used to this reaction from her) I find that adorable.
Yuri low key, grouch blushed in Yuko’s presence as she stepped in to encourage him before his performance.
Of all the people to go after Yuri after Yuuri’s performance, which made it obvious Victor was going to stay, it was Yuko. Not Victor or even her husband, but Yuko.
She tried to encourage him to stay despite him already knowing the results. He left anyways, but the gesture remains.
It’s entirely possible Yuri grew up without his mother/maternal figure nearby based on his flashback with his grandpa. It’s probably due to work/other circumstances (especially if they were poor + skating expenses + Yuri being the breadwinner).
As a result, Yuri has subconsciously latched onto Yuko as a mom figure.
Yuko, bless her, seemed to connect to Yuri in a way I don’t think Yuuri and Victor has or ever will, and it was done in a low key, subtle fashion.
Initially, I thought it was a crush on his part, but after more thought and rewatches—looks like he really misses/craves that maternal presence in his life even though he understands why his mom can’t always be around.
Those little details made the episode for me.
EDIT: For clarity and grammar.