Shakugan no Shana Things

Bikinis are typically two-piece swimsuits for women, available in many different styles and colors. It's like waterproof underwear.

A Katana is a kind of Japanese style of sword with a curved single-edged blade. Best known for speed, light weight, and cutting ability. Highly popular in many styles of manga and anime.

The character is wearing school uniform. Most probably he/she's a student.

A Swimsuit is a one-piece article of clothing that is designed for participating in different manners of water based events. Worn casually by the more modest.