Nobody's POV:
Serena quickly turn around in time as Kokushibou used his breathing technique again.

"Fourteenth Form: Catastrophe - Tenman Crescent Moon" Kokushibou said as he swing his sword.

I tried to dodge but, I got hit as I was in pain. Even, I was trying to continue to fight him.

"Serena! Get out of there! You can't fight him!" Genya said in a fear tone as they were scared for my safety. "I... I'm not... giving up yet..! Breath of the Moon Fifth Form: Moon Prism Slash!!" I said as I send the powerful move to him until I destroy one of the pillars.

"Did... Did I got him..?" I asked as I was trying to see but, there were dust everywhere until I feel pain everywhere as I fall onto the ground too. "SERENA!!!" Sanemi said as he was struggling to get up to help me. "I'm very impressed on... how far you came, Serena" I heard Kokushibou as I quickly turned to him until I was terrified of, he didn't get hit. There was no single scratch on him even, his sword change too.

"H-He's too powerful... I don't know on, how long I can fight him..." I said to myself until I hear someone. "Serena. Don't give up" I looked up, it's was mother.

"Mom..." I said as tears started to form in my eyes. "Please, don't give up. It's not time for you to leave yet. Everyone will be waiting for you to came home, Serena. Finish the job" Mother said as she gave me a warm smile until she was gone.

"No... Mom is right. I'm not leaving until... Muzan gone for good" I said to myself as I slowly stand up from floor. Sanemi, Genya, Muichiro & Gyomei were shocked of, I was still standing even, Kokushibou was shock too. "I'm not going to leave until Muzan is finally gone!" I said as the silver crystal stared to glow until I transform into my new form.

"S-Serena..." Muichiro said as he & the other three were in shock. "Breath of the Moon Seventh Form: Dark Blood Moon!!" I said as I run towards Kokushibou even, he quickly used the breathing technique.

"Sixteenth Form: Moonbow - Half Moon" Kokushibou said as I quickly dodge his attacks.

When our swords clash each other, this send a powerful wave across the infinity fortress. Kokushibou was shocked of me until his expression became angry, we continue to fight. Then I saw Sanemi & Gyomei were coming towards us as I was hold him in place.

"Guys! Cut his head now!!!" I said as both Sanemi & Gyomei cut Kokushibou's head off at the same time. Kokushibou's head turned to ashes. As, I was really glad we defeat him.