Well, if you realy want to get some help with your haremgirl explore problem, then you should describe the problem more then just with what you dit it.Suddenly I cannot manage to bring an harem girl to explore with me again...also, is there a key to show the current harem?
"It dosent work" or "Suddenly I cannot manage to bring an harem girl to explore with me again" no one can help you this way.
There are more infos needed. The more infos you can give the easyer the Dev or someone else can help you.
The "key" to show the current harem is a simple one, just give them some Love and pay attention every Monday morning during the time when the Upkeeplist is shown. You can also take a screenshot of this scene when you need to, to not forget who you recruited to your harem. And there is a computer in your bedroom with the lovely Siri you can ask her to show you the character interface. If a girl is in your harem she has a haremsymbol shown up in the nice walking animation. Maybe check this out and take a pen and paper to write down the names of the girl if for some reason you have a memory problem.
This is not a "jump and run" game, this is an artwork of a game with sexual content. This needs some respect and sure some attention to the details of this game.