The book of magic tickets are Kouta’s life (something only he and Chiro know) so even when he desperately wants more female members in the Occult Research Club, he daren’t make any more reckless wishes. But the club quickly learns that their witch-summoning was successful, putting Kouta in the unusual position of having to stop his clubmates from stalking and peeping on Rurumo as she camps in the woods.
So once again, Kouta uses the tickets to help Rurumo (to protect her honor, specifically). And by using her magic, he learned that that was what she and Chiro were doing camping in the first place: waiting for him to use it. She can’t go back to the Underworld until her training is complete, which I take to mean “until Kouta uses up all of his tickets.” In other words, she can return when he’s dead? Something to ponder going forward.
But first things first: Kouta doesn’t think it’s right for a delicate little witch like Rurumo to live like a dirty hobo, so he invites her into his home. His family consists of his mother, who knows what kind of horndog he is and is constantly staring at him, as well as his little brother and his dad (whom we don’t see). Worried by how bringing a girl home might look to his mom, he tries his best to keep it a secret. Between Rurumo’s loud slipper-shuffling and Chiro yelling in the bath, his clandestine guests don’t make it easy.
Indeed harboring a magical trainee is no cakewalk, physically or psychologically, as Kouta is so stress out about being discovered he neglects to realize that for three days he has, essentially, been “living with a girl not related to him in the same room before marriage”, which as it happens is the official SI definition of Living Together. In other words: he has arrived, at the “highest stage” of his life, almost by accident.
The bliss of sharing his room with Rurumo is all too fleeting, however, as his mom storms in the room, and…it looks bad. The situation looks like exactly what she suspects: that he’s abducted a girl and is keeping her captive in his room. Kouta only saves his mom from committing filicide by expending more tickets to magically create a cover story for Rurumo, which is that she’s his sister.
That means the whole family now accepts Rurumo’s existence in the house as perfectly normal, but it also means she gets a separate room, much to Kouta’s dismay. Still, he’s alive (and not in jail) and Rurumo is safe and secure, so he doesn’t have too much to complain about…though I wonder how many of those 666 tickets remain.