I'd like to bring your attention to something. when pikmin 3 was announced at e3 of 2012, we were shown four main characters. yet the trailer/ gameplay footage only showed the use of three characters. it appears that since the begining nintendo hinted at using only 3 captains at a time. however where does this place Delta (the name i refer char. d as). Nintendo did say that the four characters shown were the main playable characters in pikmin 3. this leads to speculation as to why nintendo may be hiding delta from us. Also is he koppaian (?) or hocotatian. we know that alph brittany an charlie are from koppai, but delta was the first in their concept art. If he is in the game, does this mean he plays a larger role than the koppaians, or as a replacement character. Like loosing louie and reciving the president. One therory of mine is that the president has retired and olimar has now become president of hocotate freight & they hire delta to go on a mission to the pikmin planet. There may be much speculation to delta, but i believe he is in the game. For they never stated that the removed a character. i hope this has brought a new view to character d's whereabouts. Just remember this, last E3 they had shown that you only control three characters at a time, yet showed four main characters.
according to loose translations of the Japanese pikmin 3 website, a few things can be concluded (credit to ymmot392 for most if not all info here)
Alph is a technician and created the ship used in the game (refered to as drake)
Brittany is a botanist sent on behalf of koppai
Charlie is the captain of then crew and has a liking towards Brittany
the game is 1-2 players
the food shortage was caused by a spike in population growth
so yeah those are the main points of the translations of the site and there is even more to come on the Japanese website thanks ymmot392 for your translations (and thanks to your friends)