Shinobu hated the idea of you becoming a demon slayer. She knows that you have a good reason to want to be a demon slayer but she couldn't lose the last family member she was left. She was calm the first time you asked but the more you asked the more mad she seemed

Shinobu faced away from you while you tried to convince her to allow the idea of you to become a demon slayer. You could do it without her permission but it seemed wrong

"No! You're too important Kanae! I-...I mean..."