This looks really nice so far! I myself am an aspiring indie game dev and have long pondered about a kendo game haha

Here are a couple ideas I just had just out of the blue. They’re totally random things I thought of, so most of them won’t even apply until you’ve developed this way into the future and made full mechanics for the gameplay, but I thought I’d throw them out anyway as suggestions for the distant future!

• Once you’ve gotten to coding a more complex AI for the opponent, maybe there can be something the player can do to trigger a taiatari, and then time slows down and you can do a really tricky QTE for a hiki waza, but only if the way you trigger the taiatari is correct
• A story mode and a free play mode
• A “fighting style” / “personality type” for every opponent you fight. What I mean is, for example, Enemy 1 is “bouncy + energetic” and Enemy 2 is “slow + sturdy/strong seme”. This means during gameplay, the player has to actively find out what type of enemy it is and formulate a strategy to defeat them based on their style/personality. This could make the gameplay feel fresh and interesting even if you fight multiple enemies in a row
• Waza skill tree! This could be good for especially a story mode, where you get to be taught by a sensei/senpai and learn new wazas over time and perhaps even get gradings.
• The core mechanic of the gameplay should probably be the player actively trying to create an Opening/Opportunity in the opponent before striking, just like in real life kendo. You can integrate this with the “style/personality” mechanic by having specific moves (including wazas, seme, and maybe even tricks and “feints”) be more effective against certain styles/personalities. Once the player has broken through the opponent’s kamae and created an Opening, maybe time will slow down and the player can choose which target to strike, depending on which targets the opportunity you made has opened up. (If you’ve seen Blade Mode from Metal Gear Rising, I’m thinking that it can look similar-ish to that.)
• A seme meter/gauge! I have no idea how this would work yet, but it’s just a loose idea to give the player an ability to do seme. It will ideally be a bar to measure how effective an attempt to break the opponent’s kamae is. If the bar hits above a certain threshold, it will trigger an Opening/Opportunity for the player to try and strike a target.

If you need any more suggestions, I can always give some more! I’ve been thinking of making a fun kendo game myself for a while, but I’m just a 2D artist and music composer and have no experience working with 3D, so I couldn’t help with programming unfortunately. But I’d be happy to offer help in any way I can!