Unfortunately, his two expressions require very clever and skillful acting, or two different makeup looks.
I would use eyeliner (black or grey) along the upper lash line, smudging it a bit. Then apply some of the same eyeliner along the outer 1/4 of the lower lash line. You can smudge liner with a q tip. For a more innocent look, keep the liner close to the outer corner of the eye. If you want a more evil look, you can extend the liner a quarter of an inch or so, and blend out. This creates a semi cat eye effect.
The Sushi Monster makeup tutorial on deviantArt is a great place to start. There are better cosplay makeup tutorials on dA than YouTube, so I'd check there first. Don't know if this helps at all. Good luck!