Japanese is widely known as a WH-in-situ language, where WH-phrases stay in their original positions. This paper shows that obligatory overt movement of WH-phrases is involved in mono ka rhetorical questions (MRQs), which are examined in Oguro 2018. After observing the behavior of MRQs suggesting that they should be regarded as negative assertions rather than questions, this paper reveals that WH-phrases in MRQs need to be obligatorily fronted to sentence initial position, by investigating the scopal interaction between WH-phrases and the particle dake 'only'. It is suggested that WH-phrases in MRQs should be treated on a par with negative phrases in negative preposing cases.