Full Immersion [for what it's worth]

Hmm. The obvious answer is yes: cooperate with Zettai, expand the party, get a partner who knows the local culture, history, and lay of the land, combat situations more likely meaning Jarod would likely level up faster and have more opportunity/reason to use his sanity sapping abilities.

On the other hand, this will make it even harder to make Jarod act crazy than it already is with two rational suggesters, as Jikkai will definitely notice his behavior and we want to stay in her and the queen's good graces for now.

Overall, >sure