The next day...

Let me put it this way; I'm not interested in watching Popotan again anytime soon!!!
While it was enjoyable sleuthing out the question ''ARE there two versions''? (see below, the answer is YES). It was also work, it was draining on me to go through 3 DVDs comparing screenshot to screenshot.
That said, I find myself in the classic ''Which came first the chicken or the egg?'' dilemma. My opinion is the series came first with the hentai game being a sequel to it. I don't discount the possiblity that it's the other way around. Which would make the series a prequel to the game.
Anime HAS been spun off of games before (perfect example: Pokemon). And the series hints at that possiblity in doing an execellent job of suggesting a possible prequel for itself. With Mea having the same role and casting a 20-something man in Ai's role (the origin of Keith perhaps?) and a boy of about 10 in the role(s) of Mai/Mii. With a tragic ending of the house burning down and perhaps one or both dying in the fire or being abandoned to a (pre-WWII) point in time.
BTW, I'm not convinced that each ''jump'' is 5 years. That was only explictly stated when Mea and Mai missed returning to the house to ''jump'' and the house teleports to the same spot 5 years into the future. I tend to think that location and time shift are a pair of varibles that are random until fixed as constants. As in Daichi finding the house as a boy and later as an adult. Purely a roll of the dice. It was clearly unintentional that the aliens would have allowed that to happen. Because Keith tried to kill the adult Daichi to preserve the secret of ''The Quest''. If there were any planning involved, Daichi would have only come across the house at only ONE location and point in time.
That's what I base my reasoning of the future Popotan on. The aliens did not know what they were teleporting into until they did it. Unlike Star Trek where exact coordinates are set before teleportation is initiated. And location is scanned to determine where a safe place is to teleport to.
In other words, the aliens have no ''crystal ball'' sight into the future. They pick a time and place at the spur of the moment, lock it in, and go. Not having any idea what they are going to find when they get there. With location being a random spot in Japan and time point also being of random length. Think ''Near Osaka, 3 years into the future'' as locations in time and space, lock those into the teleporter, and click on ''yes'' when the computer displays ''Are you sure? (Y/N)''...