"kasumi" can refer to a number of characters and a few artists. Check the current list of kasumi* tags to see if there is a more specific one that fits what you are trying to tag.

Some of the more popular tags from the list include...

Characters

kasumi_(doa)
kasumi_(garasaki)
kasumi_goto
kasumi_(nayami)
kasumi_(dreyk-daro)
kasumi_shirinami
kasumi_winters
kasumi_yoshizawa
kasumi_(liepard)
kasumi_(kurai_kitsune)

Artists

kasumibun
kasumihavok

...but check the complete list if the one you want isn't listed here.