Need help improving running animation

I tried to make a simple running animation of 2 people, through a rough field.
The problem is that it seems very clunky around the stepping part.
After using a reference of running characters from the game Genshin Impact, I recorded the running animation sideway to better reference it
I split it into 5 main key that span around 10 keyframes

I will attach a link to download the blend file I’m working on:

The 2 characters are Vroid studio models that were converted to MMD models, their format is PMX, you can use CATS plugins to import it since it comes preinstalled with MMD plugins, or you can download it from here:

This is a lot of trouble but anyone could help me, I would really appreciate it