Suki ni Sasete Miseru Kara! - Vol. 1 Ch. 4

[MangaDex]

 

[Drax99]

Even though Iwasaki-san gave up at the end I hate her. It was all planned to disturb their date

 

[dibblee]

what manga are the last pages from?
nevermind: Ushiro no Seki no Katou-kun

 

[notcishet]

Iwasaki-san is clearly just a plot device, we've seen Hiro get jealous when he saw Sun with Eita, who's an actual character when they were at the Summer Festival. This was about Shun coming to terms with his own affection to Hiro, the fact that he needed a rival to do that is important.