Maybe I'm wrong, but it seems to me that Mulan is building a really convolute plot, in which you can't simply solve a quest to start the following one, because every quest give to us some hints about Kira's past and her actual mission: the mysterious Lenny's quest; which is the main quest of the game. So every progress in a certain quest can put in question everything we thought to know, forcing us to reopen the past quests, putting what happened and how Kira interacts with the various characters in a totally different prospect.
Then there is the issue that a great part of the gamers prefer to have a great number of new sexual contents, rather than a great story and the developer must take this into account; but this is an issue of every porn game.