Hmmm... how to put this...
Do you remember the scene with Margaret explaining 'Strenght' and 'Moon' at the beginning of the episode... and how those cards appeared on Yuu's hands on the ending scene?
Kou is Strenght
Ai is Moon
By having a relationship with those two, Yuu has acquired new Personae. This were Social Links. In game they took a few months to be complete through events. The anime simply had this two pass under 2 weeks. P3 and P4 basically have a mix of 'one moment we fight monsters' and 'the next moment we have to study (daily life), have friends (Kou), get a girlfriend (Ai), work (the crane on a napkin was a reference to this)'
Also... a bit extra for those players of Atlus games. The ringtone that came out from Yuu's cellphone was "Zigeunerweisen Sarasate" - Catherine's Game Over Song... whenever you lost on Catherine the 'Love is Over' legend would appear instead of Game Over along this song. Really fitting.
As I see it... it seems only those that played the game will end up enjoying this series after all.