Judging from previous chapters, he's omnivorous, can protect himself with a cocoon of threads, and can move and hunt using them. Why does he claim he'll die without the host when he doesn't actually need one?
They have an army of several hundred fighters, they could find someone suitable for the rescue mission among them. Chopping off horns is too drastic a measure
Even on the brink of death, she didn't tell the boy anything about his parents. I hope the author came up with a worthy reason why the servants have been silent for twelve years.
@Mathiason mentioned that the protagonist received memories from a past life, by the sixth chapter I had already forgotten about it. This plot twist is still irrelevant - all the knowledge MC has demonstrated so far is easily explained by the fact that he is an adventurer with over ten years of...
And once again, “I need to become an adventurer to find information about my sister.” How about using the connections of your companion's father, the Duke, to find your sister?