Mushoku Tensei: Isekai Ittara Honki Dasu - Shitsui No Majutsushi-Hen summary:

After separating from Eris, Rudeus falls into the depths of depression. He travels to Rozenberg, the second city of the Principality of Basherant, to search for his missing mother, Zenith. Desperate, Rudeus tries to accept a high-ranking quest alone in order to make a name for himself. However, by chance, he ends up working with a party of B-rank adventurers called the Counter Arrow. One of the party members is a girl named Sara, who reminds him of Eris...!A complete manga adaptation of the seventh volume of the original novel, depicting the aftermath of Rudeus' separation from Eris!