I just saw the movie yesterday, and I totally agree. I also felt that they eased up on Ueno and just showed her as a bad person with a crush, when she has more to offer.
I wasn't a fan of all the alterations, like with how they found out Yuzuru was a girl (though honestly, they made up for it when they had Nagatsuka's hilarious reaction), and there were so many omissions. Especially, like you said, Mashiba and Kawai. Mashiba wasn't even a character in the movie; he was a plot device.
It was a good movie, but I would've enjoyed it more if I hadn't read the manga. It also ticks me off that on MAL the movie has a higher rating than the manga. Granted, the movie has about two hundred thousand additional viewers than the manga had readers. I gave the manga 9/10 and the movie 8/10. Overall would recommend, but I'd recommend people watch it before reading it. Truly a great story.
i agree with you up till your rating the manga 9/10 the movie for me at least was a 2/10 and that is me being generous
Cried a lot. I'm thinking if I should read the manga as well since the movie's weakness was with Kawai and Mashiba's friendship with Ishida. It lacked screen time and was underdeveloped. But apart from that, the whole movie was well done and just well-paced. I understood every character, apart from my issue with those two, oh and also how Ueno got involved but I understand her behavior. After all, I blame EVERYTHING on their Homeroom Teacher. Talk about causing trauma to more than two students, encouraging to poor behavior.