Ushi No Tane Forum

do u need the h.sprites to get married or anything? if theyr worthles i wood lik 2 kno

Yep. I'm pretty sure you have to meet all of them to get married.

Because I think Mark/Chelsea won't move in until you get them all. And if you don't meet all the characters you can not get married. Or something like that.

you have to unlock all of the main characters, including mark/chelsea, which means you have to have 7 harvest sprites unlocked among the other requirements needed in order to have them move in to the islands

http://www.fogu.com/hm7/basics/gettingmarried.php
I'm pretty sure you need to unlock all the areas, and yes, you need to meet all the sprites. I think so, when I tried to marry Shea, he wouldn't marry me until I had unlocked the last sprite.
the last one, you have to befriend Wada (Wada)You need to get him at like, 7 hearts before he'll let you get to the tower.
and get go through an event, then you can go to a tower where I sprite'll give you food once a day.
After that, you can marry.

the tower
scroll down a bit, it'll explain better.