It's just as good as the anime and there's almost no significant difference between them (in a good way). The movie was funnier. The anime had a greater running time, so could explore its characters and situations a bit more fully. The endings are a bit different, but I liked both and they're basically saying the same thing.
They're clearly the same story, though. Neither feels inferior to the other. I'd happily recommend either.
Once again, a 17-year-old girl (Tachibana, played by Nana Komatsu) is in love with her 45-year-old boss at work ("Tenchou", played by Yo Oizumi). She's a former track and field star who's given up running because of an achilles injury. She's also self-possessed to the point of being a bit robotic, being bad at small talk and friendliness. (She gets it from her mother.) She tends to look as if she's glaring at you.
Meanwhile he's a self-denigrating divorced loser whose negative view of himself starts with his age but has plenty more on top. His response to a girl's love confession will be to be aghast at her poor judgement and suggest that she make more friends.
The film splits quite neatly into two halves. The first half is funny and a bit awkward. The character relationships are all up in the air. The film's a rather good romantic comedy, with Tachibana and Tenchou failing to connect while other wannabe-boyfriends stick their oars in too. Even minor supporting characters like Kubo-san made me laugh. "Yes, you stink. But more importantly..."
(Their gruesome date movie is Parasyte, incidentally, rather than that zombie film from the anime. That's the 2014-15 Japanese two-part manga adaptation, obviously, not the 2019 Korean international megabuster. Either way, good choice.)
What I'd call the film's second half starts when Tenchou takes Tachibana to the library. This is more comfortable. It's nice. It's also less funny, because we're past the misunderstandings and goofy failure. This is where the characters start properly learning about each other. We see what makes Tenchou tick. We see him and Tachibana helping to heal each other. This feels more Tachibana-heavy than the anime was, with probably a 70-30 split in her favour and a strong focus on running and her former teammates, but the film doesn't neglect Tenchou and Chihiro either.
The cast are good. I've seen Yo Oizumi in quite a few films and he's always been dependable. Nana Komatsu does well at making us like and empathise with someone whose one-line description is "cold and emotionless". She was the biggest risk, since a badly chosen Tachibana could have sunk the film. She's a young actress, obviously. The anime's Tachibana was perhaps more memorable, but I have no problem at all with Komatsu and I think she did well in a role that could have gone horribly wrong. She's conveying lots of detailed emotions in a stoic character. I think I might prefer the anime's Kyan Haruka, though. Oh, and this film minimises the screen time of its child actors, which means less attention paid to Tenchou's son. It's a slight shame, but I'd have made the same decision.
It's a cute, charming film. You'll laugh in the first half, then get deeper character exploration in the second. (Not to be confused with the award-winning 1999 Japanese/French film of roughly the same name, based on the last script written by Akira Kurosawa.)