I've Been Killing Slimes for 300 Years and Maxed Out My Level

Laika's older sister Leila is getting married, so Azusa and her friends set off to visit Mount Rokko, the home of the Red Dragons. The mountain is bustling with the many Red Dragons who have gathered for the ceremony. Azusa congratulates Leila and the ceremony carries on in peace... until the Blue Dragons, a tribe with a long-standing grudge against the Red Dragons, attack in full force!