If the MC was smarter. You think he'd send the sword and his sister to live with Lilin in her shop. Seeing as Lilin is a childhood friend and someone he can trust. Shes a cursed item shop dealer, so she could watch over the sword and is use'd to handling cursed items if something goes wrong. Just some food for thought.. But the MCs brain power isnt at that level yet. I doubt from what we have seen os far, she wouldnt except looking after the sword and MCs sister. Her being hinted she likes him anyway on top of that.