Whilst there are subtle references to the MC being part of the Tenchi Muyo universe(TenchiVerse), I doubt it would be enough for anyone to think that they would need to watch the past franchise before starting this series.
Story: 6
The story itself is pretty generic and is about a boy who is summoned to a world not of his own with only his wits(and an inexhaustible amount of physical power) to help him find his way back home to Japan. One of the reasons why I've taken a liking to this series is due to having the MC play an active role with this anime compared to his spin-off predecessors when it comes to the action. Of course not a lot of people will like MC due to how much he portrays as a Gary Stu being all perfect, but that doesn't really phase too much as I had found Kenshi to be very likable opposed to past harem stereotypes.
Whilst there is an underlining plot of conspiracy and betrayal within Isekai, don't be alarmed if the imbalance throws you off from an episode tense with drama and action to than randomly switch to fanservice as all-in-all like its previous spin-offs, the focus is heavily set on its harem/ecchi genre and all part of the humor. Although I should add for an OVA where its producers could have taken advantage to a lot more fanservice and nudity, I have to respect that they didn't, as to not ruin the main focus of the plot(lacking as it was).
Art: 8
As a fan of the franchise since the early 90's, I have never been one to critique their sense of animation & design as it was usually the slap-stick comedy which had made me a TenchiVerse fan in the first place, so I was surprised and amazed with the improvement in animation since the time-gap with Tenchi Muyo GXP(last spin-off I had seen back in 2003). Although not a Miyazaki or Shinkai, Isekai no Seikishi Monogatari is pretty well animated for its time.
Sound: 5
Whilst most Tenchi Muyo anime have had an outstanding OST to back their series/OVA, unfortunately this is where I felt the series may have failed for me, which in turn eventuated my score back to a 5. OP and ED were great in their own way, I felt it just did not match the vibe which this series portrayed and BGM at times did not suit some of the moods. But please don't let that turn you off from watching the series as this does not necessarily mean a bad thing(it could probably just be me feeling nostalgic to the franchises older OST). In regards to voice actors, as I had watched the whole series in its native language, I had felt they had picked the right seiyuus as each character played their part well without sounding out of place(unlike some anime that can make you cringe just from a character opening their mouth!).
Character: 8
With an original plot outside of the Tenchi Muyo universe, I felt the characters were molded very well to fit the scenarios and as mentioned, minimal references had been borrowed off the franchise for hardcore fans out there to conspire theories to their hearts content. (10pts going to whoever guesses the cameo in episode 4)
Now for those who may have already seen this show or are half-way may think the show ranks of predictability and clichés but hey, in this day and age what anime doesn't? If you can't get past that part and enjoy the show for what it is, than it would be a waste of even watching it in the first place. Isekai doesn't try to be that next thing and is just there to be purely enjoyed (and which I believe they've done well with).
Whether the cast of girls can be classed as clichéd, I have to admit that they have been played well and their parts not as overused as what you'd normally see from a typical harem cast(eg.the tsundere type that's too tsun-tsun or the love-love type who smothers the hero too much).
While the cast is too many to mention(just check Wiki if you like to know more), what I will mention is that if you like your Gary Stu's(opposed to the uninspiring stereotype you get in harems), than you will definitely like this series as Kenshi is what you would call a one-man army with his exceptional skills whether they be domestic or on the battlefield.
Enjoyment and OverAll: 8
Whilst I'm not as big a fan of harem anime as I use to(only few harems I still enjoy to this day), when I did watch them I'd always hope that the protagonist gets "all" instead of having to choose only one girl(why make one happy when you can make them all right?). Yes its unrealistic, but you don't watch a harem let alone a harem fantasy for realism, and for a franchise that practices polygamy as a norm, I believe any hot blooded male shouldn't have any room to complain.
Like I earlier mentioned this review will sound very biased(especially after mentioning that I'm a huge fan), so I can only say this: watch the series for yourself if your into the following genres - harem, action, likable overpowered characters and slap-stick comedy, I can guarantee that you will like Isekai no Seikishi Monogatari.
