I'm confused about one thing - if Taichi is the only human, what the hell are the knight, big tiddy onee-san, and the old folks? Remember, the knight and older girl both referred to him as being a different race than them.
@CelticMutt The author hasn't revealed what race Nina is yet, but Krusche is part of a 'female knight race'. There's not much details on that either, but I guess you can assume that they probably have better attributes than normal humans. To put it simply, Taichi is like a villager in everyone's eyes.