Lost name of multi book series about a girl knight and a bipolar guy
found it!

http://www.amazon.co.uk/Aqua-Knight-v-Yukito-Kishiro/dp/1569316341/ref=sr_1_1?ie=UTF8&amp;qid=1398461089&amp;sr=8-1&amp;keywords=aqua+knight

Aqua Knight - Yukito Kishiro