Giving the theme, fan service should actually be expected. I mean, the plot itself besides being cliched, it is aimed towards young males. Even if women do read this, men are still the majority.
If the plot was just less cliched or was aimed towards young teens, like 10 to 12 years old with a very light hearted adventure theme, then fan service wouldn't be needed.
Problem is why most mangaka can't think of anything else other than tentacles and slimes if what they want to do is taking off the female's clothes and give some ecchi. Another problem is why most Japanese manga hypersexualize women to the max? This manga is not even an ecchi or hentai. This is why other part of the world always think that most Japanese are perverts. Can only think with their dicks and love loli.
( ̄へ ̄)another fan service chapter..... slime tentacle + half naked sexy girl .. oh c'mon, thought this manga was better than the other rpg themed manga out there..it was good in the beginning and i won't they that but.. *sigh*