"Ko" can refer to several things. A more specific tag should be used instead.

Concepts

• k.o. - Caption, usually a video game caption.
• unconscious

Artists

• ko_(hetarenoko) - Pixiv display name is "KO(ケーオー)".
• ko_(kobomb) - Goes by "ko" on FurAffinity.
• ko_takeuchi - Signs work "ko".
• kokosimon - Pixiv display name is "ko".

Characters

• ko_(fabio_paulino) - Kangaroo character created by Fabio Paulino/Linno/Zebala.
• ko_(kodus) - Kobold character created by kodus.
• ko_(okami) - Dog character from Capcom's Okami.
• ko_(otlan) - Kangaroo character created by Otlan.