To be clear, I haven't finished this particular WN series (at over 900 chapters, all of them of reasonable length, that would take a long time).  I have gotten around halfway through the story, enough to get a solid impression of how this is going to go.  Like most of the LNs/WNs I have been reading lately, it is an isekai story.  This particular story has a different approach compared to the ones I've posted about so far.  First, this story doesn't have a specific antagonist or group of antagonists to worry about.  The protagonist is too whimsical to really be considered solidly on any side in particular (very much an amoral type, except when it comes to women) except his own and those of the people he likes at any given moment.  

Shuuya, the protagonist, is, at first glance, your common isekai reincarnation protagonist.  However, he quickly diverges from the classic style in that he neither clings to his Japanese mores nor does he become an amoral half-villain.  Instead, he becomes a freedom-loving adventurer who pretty much does whatever he wants to.  His partner, the black cat with tentacles, Rorodine, is an adorable mascot character who can be easily compared to her partner in terms of whimsical behavior (typical cat behavior a lot of the time).   By the point of the story I'm at, Shuuya has a rather massive circle of allies, friends, and subordinates (as in triple digits), so one thing that most will have trouble with is keeping his list of lovers, wives, friends, and family straight.  Actually, keeping them straight is pretty close to impossible, since he never seems to stop adding to it.  

Because of his mercurial nature, you might think that Shuuya would be considered insincere, but he is the type that keeps a promise once made, no matter what it might require of him.  Because he picked a half-vampire type of race, he doesn't need to worry about aging, so he naturally takes a long-term view on how life will turn out in the end, not hesitating to make friends and enemies along the way.  There are a ton of actually well-written combat scenes (with an increasingly odd combat style as the story goes along) in this story, and that is one of the attractions, since Shuuya is always looking to improve himself along the way and loves nothing more than testing out his skills.  

However, the very whimsical nature of Shuuya's behavior becomes more and more of an issue later on.  The feeling that nothing is happening for chapters even though a lot of things are happening begins to press down on you, and I actually started to burn out on this story somewhere around the 200 chapters mark.