The Legendary Hero Is Dead!: The Land of the Gods
 

In another world altogether, a random guy from Earth gets pulled into the story as a new hero whose party is unfortunately slaughtered. He runs into Kyle, Millie, and Diego; who have been traveling through dimensions looking for powerful opponents to fight. The isekai hero explains that this new world is also under the threat of a Demon Lord, and reveals his own Holy Sword has the ability to access the Divine Realm where the dead dwell alongside the Gods. Intrigued, Kyle sends word back home to recruit some backup.

Having defeated Larkvlad 4 years ago, Touka Scott is enjoying the slow life with Anri, Yuna, Diana, and Ethel now living in his house. After receiving Kyle's message, our thigh-loving hero heads to the capital to fetch former Princess Marguerite, and the old gang sets off on a brand new adventure!

After effortlessly crushing the other world's Demon Army, everybody is shocked to discover that the Demon Lord has already been killed by Leland Tallman, the crazy bone fetish doctor from the original series. Now with powers far surpassing Larkvlad, Leland drives back our heroes and assaults the Divine Realm with Touka and company in pursuit!

I need to read this.