These two series have only one thing in common, and that is the fact that the setting in which shiniki is sucked into is what one would consider a game world. This recommendation is for those who like the Game genre.
Death march is about a MC who supposedly dies and is sent to another world with 3 cheat items which he uses right off the bat and becomes a super OP character like Momonga is in Overlord they both share comedy and adventure and I think he Harem aspect too.
Both stories are pretty similar, they start with a japanese guy being transported to another world and being overpowered from the very start. Also, both male MCs travel around the world defeating monsters and going on adventures.
Both of these are about a guy getting stuck in a game world. Both MC are OP. Major differences are that "Death March kara Hajimaru Isekai Kyousoukyoku" had a single skill which caused the MCs OP and "Yasei no Last Boss ga Arawareta!: Kokuyoku no Haou" has a MC that end up as his female character.
Both are set in a fantasy world. "Death March kara Hajimaru Isekai Kyousoukyoku" is about a man that gets stuck in a game as a younger version of himself and uses a meteor skill that causes him to level quickly and become OP. "Koushaku Reijou no Tashinami" is about a girl getting reborn into an Otome Game as the villianess and avoids her fate and uses her old world knowledge to better the land her father hands to her.
Both hero are summoned to the new world not by dying. Both are adventuring from city to city with their companion. Both of the heroes are clever type that can think wisely and make reasonable decision. Both have girls companion as a usual trope for any isekai novel. The science behind both magical world is a bit difference but interesting to learn as. <br/>
While the mc in Death March is like a part time hero doing sightseeing while sometimes defeating extremely powerful enemy(definitely feels like One Punch Man if Saitama starts doing an adventure), Tsuki Ga Michibiku is more like a god hiding himself to become normal human and relying his overpowerful companion to finish the task given.  read more