Kaizen was impressing everyone with his skills, but to him his current level of strength was nowhere near what he had hoped to achieve.
In the midst of the fight against Teshi, he realized how far behind the strongest players on Midgard, let alone all the worlds of Rise Online, in terms of stats.
At all times, Kaizen needed to keep his distance from Teshi, because even if he used <Giant's Lungs> to double his physical attributes, a single sword strike from Teshi would probably be enough to leave him red-faced. Moreover, to make Psyker's job more difficult, there were few opportunities for effective attacks that arose, so all he was doing was spraying arrows at his enemy.