I recommend you watch this as an introduction to the other shows because this movie simply looks unbelievable, one of the horse girls is named after Tachyon a hypothetical particle that travels faster than light. It's one of the best names in the Umamusume Cinematic Universe because not only does the insane sakuga look like she's actually running faster than light, she's also one of the coolest horse girl character concepts, by that I mean I desperately want to get Tachyon action figures or something to play with.

Other characters are also extremely cool, protagonist Jungle Pocket is like an ammeter underground runner turning professional, drastically different from MCs in other series in both origin and personality. Fuji Kiseki is the inspirational horse girl looked up to by the MC like in other shows, again with her own interesting twists. Trainer Tanabe is not very intersting as a character but I love his backstory. You see he's a "legendary" trainer and Fuji Kiseki trusts his skills very much, yet he's never had a derby win. This puts into perspective just how difficult it is to have a derby win, never mind multiple derby wins, which is very important because the TV series is called "Pretty Derby".

BTW I also had to look this up myself, but a "derby" is age-restricted horse race, you have to be exactly 3 years old so there are no do-overs, everyone gets only year to win against all the other best horses in the sport.

There is unfortunately no deep story or meaning, just your generic "never give up" kind of thing but presented well with a minor twist. However that doesn't matter because you can find plenty of deeper meanings from the rest of UCU shows.

If you're still not convinced, I too back in 2018 thought horse girls is a desperate attempt to grab a slice of the ship girls gatcha game craze, so I didn't watch it. I couldn't be more wrong, horse girls is a great idea compared to just realistic track&field athlete for many reasons.

The outfits, it may sound stupid but I love the fancy race outfits. They're totally impractical of course, so they will never work on a realistic setting but they do on horse girls, because Umamusume does not take itself too seriously. These outfits are simply cool to look at and they accentuate the personalities of the characters to excellent effect, even the ones you've never seen until the race, because the outfit tells you a mini story visually.

The world building is just light hearted fun, for example horse girl traffic lanes!

Horse girls also get various carrot based special dishes which look questionable to me but hey maybe they love it because they're horse girls!

Even just the physique itself, if you look for a real world 1000m foot race you'll quickly discover they're just jogging most of the time, I'm sure they jog much faster than I can sprint but it's just not very exciting. Horse girls on the other hand are sprinting at superhuman speeds right out of the gate and as mentioned before, go faster than light at the final stretch, just looks way more dramatic.

bonus point for extreme quality of presentation