Just finished the game and I loved it. I think that the possibilities of updates/DLCs are infinite.
Here's a few ideas for the dev what he could implement on the next updates:
1- More SMS messages (this is the feature of this game that I like most)
2- SMS history so we can see previous chat without having to redo the game.
3- Implement the "live" button, I'm sure it will be a game changer. Also after a while we should make money doing porn with Chiho.
4- Never ending mode: After the onsen, Chiho and Shota go back to the apartment. Shota surrender to the cuckold lifestyle to stay with Chiho. The onsen becomes a place that you can visit just like the city.
5- Alice minigame should be sexually related just like Chiho's dog walk or the exhibitionist one. Also complete her story and give us a way to cuck her "bf".
6- Develop the onsen secondary characters.
7- Some 2d pixel sexual positions with pregnant Chiho.
8- Bimbofication of Chiho, make her a slut with piercings and tattoos as she gets corrupted.
9- More positions exploring the other rooms of MC's and Chiho's appartement.
10- A way to fuck Shota's mom (maybe she visits her son and discover he is a cuckold and MC seduces her)
11- Let Shota's boss and work colleagues fuck Chiho.
12- Shota's dad fuck Chiho.
I can think of many different ideas that could be used in this game because it has so much potential.
PS: Buy the game if you like it, this way you're motivating devs to create more content for you.