Kaiser was smart to recognize that the Ruby Dragon underestimated him and used that to his advantage. Using the actual skill as the cover, he shot two blades, following the skill. The target was the eyes, which would give him even more advantage.
As the Ruby Dragon roared in pain, Kaiser did not miss the opportunity. He leaped into the air, reaching above the Ruby Dragon. He turned his body around and landed on the Ruby Dragon's back. The first thing Kaiser did was not to cut the Ruby Dragon's neck but the wing.
The dragon had an overwhelming advantage because it could fly, and it would be hard for Kaiser to attack the flying dragon with his ability. Removing the dragon's ability to fly would give him more chances to win the fight. He planned to fight the dragon, not survive for twenty minutes.