Tensei shitara Ken deshita

If seeing cute characters doing absurd things and facing off against absurd enemies and triumphing is interesting to you, then both these animes would be enjoyable. The brutal and amoral (chaotic) nature of the world these anime are set in provides a somewhat niche enhancement to the immersion and investment into the anime and development of the MCs (Fran and Kumoko respectively) 

It'd be pretty obvious ofc, Reincarnated as a Slime and Sword are closely similar to each other. They have the following: -The title itself is closely related to each other. -Both MCs have same skill but in different approach. -Skill sets are quite same too. -Monster hierarchy are pretty much the same. Overall, if you enjoy watching a unique isekai anime with vast powers, skills and wild adventures, then its a must watch!  

Ken Deshita and Log Horizon both have main characters who wake up in a different world and goes to adventure with a loli girl who looks up to them. Both have a laid-back tone with some cool MC moments with loli girl training to get better. Both anime share the same director and sound director as well. If you're a fan of Log Horizon or RPG/game/fantasy world with adventurers, guilds, monsters, etc you'll like Ken Deshita.  

in the anime Boushoku no Berserk, just like in Tensei shitara Ken deshita, the partner is a sword, however, unlike the anime Tensei shitara Ken deshita in this anime, the weapon itself has several forms for support and attack, as well as in both anime, the guns themselves talk and become stronger in both anime there are characteristics for leveling and raising the level, also, the main character himself also becomes stronger, makes friendly acquaintances and tries to protect everyone, as well as hide his real strength so that others cannot find out. 

- main characters are male and female with brother-sister type relationship - both main characters are strong and cooperate to win together - main characters begin from zero (no money and status) and are underestimated by some folks, but change minds after taking part in action - both animes touch the subject of getting back the pride of some nation that is considered the weakest among the others in a fantasy world 

both are new ridiculous ideas but nicely done.  

The system and everything else except for the art style is a massive uplift. This is what an isekai should be like. 

Mushoku Tensei and Reincarnated as a Sword are both Isekai anime series that revolve around the theme of reincarnation. Both anime feature protagonists who have been transported to a new world and must adapt to their new surroundings. The protagonists possess unique abilities and magical powers that they use to navigate their new world. Both anime series showcase a well-developed magic system that plays a crucial role in the plot. The anime series are full of action-packed scenes that are sure to keep viewers on the edge of their seats. Both anime series feature character growth and development, as the protagonists learn to overcome their weaknesses and become stronger. The anime series have a large fan base, indicating that they are popular among fans of the Isekai genre. The anime series are visually stunning, featuring impressive animation and detailed world-building. Mushoku Tensei takes a more mature and serious approach in its storytelling, making it an appealing option for those looking for a more complex and thought-provoking narrative. The anime series are both entertaining and engaging, making them great options for anyone looking to escape into a new fantasy world. Viewers who enjoyed Reincarnated as a Sword are likely to enjoy Mushoku Tensei due to their similarities in theme and execution. But what I really like is their animation, and plot as they are both not just revenge plot stories and kinda like slice of life in another world. read more 

Very similar, but the stories go to very different directions. The magic sistem si very well explained in Tensei shitara ken deshita and both series are very fun to watch. 

In both animes, the girl carries the magical object with the main character, able to communicate with her and gives her power. At the same time, the girls who use the magical object in both anime are short and loli (relatively) 

I would say there are some similarities if you are looking for a cute small girl with a cat ear themed character setting.  

In general those shows are lightweight action-packed RPG-style fantasy adventure (with a piece of gore, sometimes) where main character somewhat differs from run-of-the-mill japaneese schoolboy. Main similarities: MC quickly became OP and almost never thinks about their previous life. They must hide their identity and team up with a girl to enjoy the life in new world as your regular adventurers. Both shows doesn't try to be more than they are, wich is good. But both practiculary doesn't dig "What if?"-theme from their title names, which can be dissapointing. Diferencies: The Skeleton is a big brother-like companion to tsunderish elfgirl, while the Sword is a teacher-like for childish catgirl. Sword makes food, Skeleton eats food. The Skeleton mostly fights against evil guys, while the Sword is just a monster-slasher (poor little things...). "Gaikotsu Kishi..." is more comedy-ish show with obvious gags and references, while "Tensei shitara..." doesn't touch those themes at all. read more 

Sentient weapons in a magical world. Seiken no Blacksmith has a better, simpler story without gamification. A bit ecchi. 

Both shows are about two characters who are very different and have a teacher-student kind of relationship about how the student will grow as a character. We can see how Fran is slowly growing as a swordswoman with the teacher's advice and so does Chise, who learns how to use magic from Elias. 

Both Isekais have a prominent secondary character who is a cute beastman girl who is the MC's sword in fights and otherwise a "Must protect" character. If you loved Rapthalia from Shield hero and are a beastman/demi-human simp like me, then "Reincarnated as a sword" is a must-watch since you will see Fran, a cure cat girl wield the MC, who is a sword! 

Sentient weapons in a magical world. Erementar Gerad is more a serious classical fantasy story with some moral exploration. 

Isekai anime with protagonists wielding a sentient magical sword. In Zero no Tsukaima, the main character gets a hold of an ancient legendary sword not too long after having been summoned in another world; in Tensei shitara Ken Deshita, the main character gets reincarnated into an intelligent sword in another world and finds someone to wield them. They're helpful in battle as well as in everyday situations. Their wielders treat them like friends. 

Cute small girl struggling at life in a Medieval Fantasy world receives better treatment and becomes wholesome. Emotional and Lovely!