a nervous system

(slang) denpa-kei person: one who acts strangely (disconnected from reality), often having wild fantasies and often saying strange things

aggressive in relationships

dynamical system

(slang, derogatory) A vague, derogatory label applied to stories that have overdone, clichéd elements. Usually an isekai story with elements like those described at 異世界#Usage notes.

Short for スピリチュアル系.

being a follower of New Age spirituality

A person not interested in marriage or dating; a person who is considered insufficiently assertive / A man deemed insufficiently masculine or manly

the imperial family line

inertial frame of reference