I think "Moai Kid" would fit better than "Mr. Moai". As pointed in other thread, -kun can be used with both genders, at all ages (often towards a younger person), but definetively with a deeper intimacy than the formal "mister".
Moai-kun sounds like he's a young boy (or girl also, but let's suppose it's a male moai xD)
The story in the pages 3~4 goes like this:
Moai World, the world where the peace-loving Moais live happily.
But one day, something happened in Puchi Land, the place where the childrens of the Moai families (called Pucchis) live. The Evil Emperor "Skull King" kidnaped them!
Despite he being a member of the Moais himself, he's the mad head of the Skull Empire which invades and destroys other lands. But after living 3000 years, only his old white bones and a few more days of life remains. Then he made a pact with the Demon to recover a young flesh like he once had. He could get it if in return he offers hundreds of little lively Moais children (pucchis).
When the moai hero "Moai Kid" knew of this, he went alone to the Skull Empire to save the Pucchis.
But the pucchis are being confined in different places inside the Empire, and the underlings of Skull King had placed traps everywhere. But Moai Kid won't give up over that. He will save the Pucchis as fast as possible and stop Skull King' ambition!