Cancer
the crab, June 22 - July 22

"Emotional and loving
Intuitive and imaginative
Shrewd and cautious
Protective and sympathetic

Changeable and moody
Overemotional and touchy
Clinging and unable to let go"

Outwardly they can appear formidable - thick-skinned, unemotional, uncompromising, obstinately tenacious, purposeful, energetic, shrewd, intuitive and wise, sometimes with a philosophical profundity of thought verging on inspiration. Their intimates, however, may see a very different character, one with a sympathetic and kindly sensitivity to other people, especially those they love.

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According to that website, the horoscope cancer isn't really something that would fit Tatsuki because personality wise, Tatsuki is not a person who is self absorbed in her own fantasies. Though probably characters like, emotional, loving, protective and sympathetic are something that would fit her very well.

Once again, Kubo-sensei hasn't allow enough screen time for this wonderful character to develop.