This kanji means clean and pure. The left part of the character stands for water and the right part does blue. It describes clear water.
Mizu is water. So SHIMIZU means pure water, clear water. This is one of the most common family names in Japan and you’ll meet many Shimizu san when you come to Japan.
This kanji means crystal clear, no hesitation. Every kanji of Shimizu Kiyoko’s name has sharp and cool impressions and I think it matches her personality well.
Actually, there’s a scene in which Yamamoto Taketora hears Kiyoko’s name and says “Wow! Her name describes herself!”
KO means a child and this kanji is frequently used for girl names in Japan. My name Junko also includes this KO 😀