I remember the plot mostly but not the name of it. It begins with a boy that came from another world recruited by missionaries that have a mission of killing a princess before she gets to the "holy land".
- They all have mechas but the boys is more like a lizard mecha
- There are different races including Elves
- They go to a school at the holy land
- He wins a race against the Elves warrior and get their princesses hand in marriage
- The boy works as a jack-of-all-trades in the school
- It looks like an all girls school