Can't remember what this one is called.

The main character is a shut-in who wants to play video games. His old childhood friend, who used to be sick and could only hear about the outdoors from the books he read to her, suddenly comes over one day and begs him to go outside with her. They go hiking, explore abandoned places, catch bugs, and she wears a skin suit the whole time.

Saguri-chan Tankentai! It's one of my favorites, the color pages are beautiful.

That's it!!! Thank you