熱すぎる監視員さんに水着を着せよう！ / メタリックスチール

This is a story about Maid Gardevoir and Kirlia-senpai going to the beach because it's too hot. They go to cool off, but find the lifeguard Sawblaze to be unusually hot, so they make Sawblaze wear a swimsuit to cool down and somehow they all end up having passionate beach sex.
This is one book in the Maid Gardevoir series, but it's written so that it can be enjoyed even if you haven't read the previous books.