I honestly have no idea what manga this is or when did i read it
I was in the same boat. I started reading this latest chapter and had absolutely no idea what was going on and nothing was coming back to me...
But the basic premise that I'm remembering after re-reading the first few chapters:
edit: finished my re-read
The MC ("Hikaru") takes over the body of some dead guy in exchange for killing someone. MC becomes a powerful assassin with his use of his points on his "soul board" / skill tree system, which almost immediately gives the power to hide in plain sight right in front of someone. That also lets him be completely broken as an adventurer since he can sneak up on things very easily, or just harvest plants while the big bad monsters can't even see him.
When he kills the bad guy, the bad guy's daughter ("Lavia") notices the murder and tells him how to escape. But then she gets blamed as the culprit of the murder. Because he can't let his savior get imprisoned / executed for this, he rescues her...
Using his powers and lots of planning and some favors called in at the thieves guild, he rescues Lavia from a locked cart while the hired adventurer guards don't notice a thing. While walking back to town, MC notices a powerful knight rushing up the road to try to catch up to the cart. MC assassinates the guy's horse with a pebble to slow him down, and some other impromptu fighting.
MC and Lavia make it back to town, they have seggs... Lavia wants to become an adventurer, so MC starts assisting her towards that while trying to also avoid any suspicion about how he might have been involved in her rescue.
Summary of recent chapters is that there is a dungeon ("Forest of Death") that overflowed. The kingdom decided to abandon the dungeon and the nearby village ("Menelka") and declare that C-rank and above adventurers are not allowed to be sent to that dungeon. The B-rank, all-female party "Four Eastern Stars" decides to ignore that and go help anyway. MC and Lavia also show up.
MC on his own goes to invade the dungeon to try and defeat the dungeon master with his stealth skills, while everyone else is defending the town.
Apparently the dungeon has two dragons, one is attacking the village, and one is still in the dungeon guarding a room that the MC just entered. <end of chapter 18>