The reason for a happy ending for this ep is that was what Narumoel got for her deeds. All she did was to protect the girls from the school so that they won't suffer like her best friend. All that was a good deed. And guess what?? Nanno is karma. If you do good, good karma will come. Narumoel loved her best friend (yes, she is les), and at the end she found her true love. This happened the same in Girl From Nowhere ep 8 Lost And Found, in TK's situation. All this boy did was to have his father's attention, and he was willing to have all the bad results to himself instead of Nanno, that's why Nanno gave them happy endings. They all have the same characteristics, taking all responsibilites and consequences from what they did and not trying to run away from it. Those were all good deeds and they deserve happy endings.