@AnekiGX I agree with you about Fukiishi; she doesn't know the whole situation with Seiichi's family, and didn't give a single thought about Seiichi's father or other relatives. Admittedly, kids (teenagers) can be pretty impulsive, but what she's proposing is an impossibility, all things considered.
Damn, her biting her nail off is supposed to show him that right know she's capable of self harm and by going away she's making him choose, stay with the girl or go after your mother, she is a master-mind when it comes to manipulation...
Honestly my nail has cracked like that before and let me tell you the pain is abnormally just really bad. She must be a strong person or maybe part of being insane is getting more pain suppressing chemicals and endorphins