Toeto is basically somewhere between a tamagochi and a raising sim, starring Luka - sorry, Toeto. It's a much longer experience compared to *Hello, Planet., and the game kinda punishes you if you try to rush through it. The end-goal is to find the Seed of Courage. This interview boasts about 24 hours of playtime.
There's a few things you can do with Toeto. You can talk to her (either by selecting the first menu option, pressing circle, or even just sitting idly), you can teach her words, and you can play minigames (which you gradually unlock by... I think meeting certain thresholds?). So far, I've found three: Shiritori (a word-chain game), two variants of Rock Paper Scissors (the first is just RPS, the second adds "Acchi Muite Hoi"), and a Rhythm Game (where you play an exclusive song by Toraboruta, "Ai Mai Hentou") which seems to have 3 levels (probably based on difficulty?). I believe there's a fourth minigame based on what I've found by poking in the files, but I don't know what it is or how to play it.
You can also go places! There are five locations (besides the white home), three of which have NPCs. They are: the meadow (Len lives there), the riverbed, the mountains, the beach (Rin lives there), and the flower field (Miku lives there). The NPCs will give hints and play with Toeto. If Toeto beats them in minigames, they'll give you items (usually seeds, but sometimes cosmetic items like hats and dresses).
There's one more thing you can do, and that's growing plants. You have to be really careful to neither neglect nor overwater them, or else they'll wither. It's kind of tedious and anxiety inducing. If a plant does wither, you'll have to overwater it for about five minutes to make it disappear so you can plant something else in its place.
There are 12 hats, 12 dresses, and 12 seeds (including the Seed of Courage). Most of them are unlocked through playing games with the NPCs, but I think some might be unlocked by meeting certain thresholds (like teaching Toeto a certain number of words, growing some amount of plants, playing minigames, talking, etc). I feel like there's probably a progression system, but part of me thinks it's random.
I think the Seed of Courage unlocks when you've successfully grown all other plants? It's possible to get it before unlocking all the hats and dresses, and you get seeds at a higher rate than anything else, so... Question marks are things I haven't unlocked.