Mizutani is a top Japanese player with a very fluid and spinny underspin/sidespin serve. Here is a video of his serve and some tips on how he does it.
4 things important to get the ball to bounce back to net.

1) impact the ball at the BOTTOM, maybe even a tad in front of bottom.
2) impact the ball higher than net height
3) impact the ball with racket speed generated by loose arm/wrist, some help from body, and wrist snap. It’s all about timing & acceleration.
4) Make 1st bounce 2/3 the way to net for extreme short, closer to 1/2 for ghost serve that bounces deeper and still comes back.

Controlling the height over net is tricky with this serve and not as high % for even a pro, so you don’t see these extreme short serves at the pro level, too much chance to get flip killed.