The World's Finest Assassin Gets Reincarnated in Another World as an Aristocrat, Vol. 5 LN

Summary

After defeating the third demon and parting ways with Noish, who fell to darkness,
Lugh and company return to Tuatha De. Although their success increases their esteem
with the crown, it also draws the envy of the nobility, who subsequently begin to plot
against the Tuatha De family. Yet, as Lugh concocts a series of assassinations against
both the demons and the humans seeking to sabotage him, he falls into a deep sleep,
where he reunites with the Goddess of Beginnings. Something in that beguiling smile
of hers suggests she has ulterior motives...