Koushirou is my best friend.

Kou Sennen is my best friend.

Photochemistry is a branch of science that studies how chemical reactions proceed under the influence of light.

The photoelectric effect is a phenomenon where a material emits electrons after absorbing light.

His long talk is just like 'a hundred days of sermonizing without a fart.'

He continued to hide his talents as if to hide his light and conceal his tracks.