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?). There are five minigames in total:
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 Flower 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'm not sure how you unlock the seed of the Flower of Courage, one of the NPCs just gave it to me for some reason. I assume I met some sort of threshold, maybe number of words taught or games played. Or plants grown. At any rate, I'm holding off on planting it since I haven't unlocked all the hats and dresses yet.
Question marks are items I've yet to unlock.