She is not without kindness either, and displays warmth towards those in the Uesugi army and concern for her allies. She isn't humorless, however, and has been known to act sassy towards both enemies and allies alike. She clearly takes her job seriously and is powerful enough on the battlefield to be called a " goddess" by some Uesugi retainers. That being said, Kasuga can be rather dour whether on the job or not. However, if Kenshin goes too far with their compliments, Kasuga may have one of her episodes. When alone around Kenshin and not on the job, she tends to be quite amiable-but can become very reserved when Kenshin dotes upon her. When these things occur, sometimes other notice and find amusement, while at other times those around simply brush it off. Kasuga often gushes about her lord Kenshin, going so far as to have " delusional" hallucinations where she calls out their name as she braces herself tightly. In Sengoku BASARA 4 Sumeragi, Sasuke says that ninja from their village must shed their humanity he then says that it was when she entered Kenshin's employ that she "became human" again, due to the love she felt for her master- in comparison, Sasuke " became human" due to having Kasuga to worry about back in their village. From then on, Kasuga served Kenshin and became their most loyal ninja. However, because of her failure to assassinate Uesugi, she was exiled from her village.
Kenshin pardoned her and took her in as a spy. However, before she could kill Kenshin, Kasuga fell in love with the warlord.
Eventually she was sent on a mission to kill Uesugi Kenshin. Kasuga was originally from the same ninja village as Sarutobi Sasuke, and the two had an amiable relationship.