YOU SAID:

I am a man of simple interests

INTO JAPANESE

私は単純な関心を持っている

BACK INTO ENGLISH

I have a simple interest

INTO JAPANESE

単純に興味がある

BACK INTO ENGLISH

I'm simply interested.

INTO JAPANESE

私は単に興味があります。

BACK INTO ENGLISH

I'm just interested.

INTO JAPANESE

興味があっただけ。

BACK INTO ENGLISH

I'm just interested.