[Manga Spoilers](/s "I disagree, Fat Masamune showing up, in a way, made Neko's arc a lot more sense.
Neko's Warning. "Are you going to go the same path as me? Will we reach the same place?" What happened at princess confession? Makabe got rejected same way Neko got rejected.
Substitute Neko with Makabe. What Makabe experienced during the culture festival arc is probably what Neko also experienced, author was obviously drawing a parallel. EVEN WITH THE KISS. Neko took Makabe's first kiss, Makabe took Aki's first kiss
Also... The dragging of fat Masamune arc is ABSOLUTELY NECESSARY. Without it we won't have the Princess Confession (Also we won't have an antagonist. If you noticed, the show always have an antagonist or people who creates problem for the MC: 1. Aki, 2. Neko, 3. Gasou, 4. Yoshino). You have to consider why the princess confession happened. The reason it happened is because Aki decided to choose fake Masamune over Makabe. Makabe's persistent courtship towards her is making her feelings for fake Masamune waver, so she decided to officially reject him. Also, she probably expected Makabe to be like "Ok, I understand" because she was being honest and genuine at that time. It is also important to take note that after the cultural festival Gasou's influence to the story is toned down a lot because her influence to Aki was severely weakened due to her failure at the culture festival. But in the end she still chooses her first love (old masamune) over Makabe.
Now imagine if Gasou got exposed at the end of the culture festival arc. It will turn to the usual RomCom after that or they have to introduce another character who would just fill the role that Gasou left vacant.
If we had it the other way with Gasou not dragging, the story for me wouldn't be as interesting because it would've gone to the usual story with Aki being tsundere maybe.
Lastly if we didn't have "Princess Confession" we won't have Masamune-Kun no Revenge at the end of princess confession. Technically at that time he had his revenge cause he broke her heart, just not in the way he wanted too.")