After a fight Hayate, Nagi heads to the apartment complex to hang out.  But her “little sister” is the only one home.  This might be Nagi’s chance to find out what Ruri’s real goal is. 
I don't need a reason to help someone.
No necesito una razón para ayudar a alguien.
No necesito ninguna razón para ayudar a alguien.
Eu não preciso de motivos
 para ajudar alguém.