His obsession with studying with studying stems from wanting to beat Hiro and go out with her, but now that they’re in a relationship I think he shouldn’t be so obsessed with it, here he’s shown wanting to impress her again by beating her, but to that just shows he more obsessed with the idea of winning rather than trying to prove himself any other way, kinda close to obsession. Furthermore, Nagi constant nagging is just who he is and how he grew up, and her it show that Erika recognizes this and accept him for him, and shown by she glad he had changed and how shes able to a difference between the two siblings. This was also shown during the Okinawa arc when Erika confesses to hiro that despite how he is she loves him for him. To me just says how much more compatible they are as with Hiro nagi never acts his true self( nagging and voicing his own opinion)I know author was going for "Erika's changed and that got Nagi's attention", but it just looks stupid. She's the same crap as always and wants her adopted brother, showing just how much she and Sachi are the very same and therefore redundant. Nagi himself seems to have no discernible rhyme or reason. When was he shown as so stingy? Wasn't he simply obsessed with studying?
But his thing with winning stays on, even now he and Segawa like to compete. That's an aspect in common they have. Stuff like that makes it a bit more believable that one likes the other. He doesn't nag Hiro because he doesn't need to wash her clothes or make her food, for starters.His obsession with studying with studying stems from wanting to beat Hiro and go out with her, but now that they’re in a relationship I think he shouldn’t be so obsessed with it, here he’s shown wanting to impress her again by beating her, but to that just shows he more obsessed with the idea of winning rather than trying to prove himself any other way, kinda close to obsession. Furthermore, Nagi constant nagging is just who he is and how he grew up, and her it show that Erika recognizes this and accept him for him, and shown by she glad he had changed and how shes able to a difference between the two siblings. This was also shown during the Okinawa arc when Erika confesses to hiro that despite how he is she loves him for him. To me just says how much more compatible they are as with Hiro nagi never acts his true self( nagging and voicing his own opinion)
I agree. I think Sachi was going by looks while Erika was looking deeper this trip.I think the chapter is meant to highlight how Nagi and Sousuke respond to Erika differently like where Sousuke would've been delighted by the lights and Nagi focused on the wasted electricity or where Sousuke would've cherished taking a trip to shop for New Years and Nagi preferred buying decorations for multiple holidays during a single shopping trip to save time.
Notice how the end of the chapter focused on how Erika perceived differences in Sousuke and Nagi's behavior that Sachi couldn't recognize.