noun
traditionalist
A person who adheres to tradition, often in cultural, political, or religious contexts.
彼は伝統主義者で、古い習慣を大切にしている。
He is a traditionalist and values old customs.
保守主義者 is a conservative, often in a political sense, while 伝統主義者 emphasizes adherence to tradition itself.
Compound of 伝統 (tradition) + 主義 (principle, -ism) + 者 (person).