It is two women, he perceives them both as women, and he has lust.

If the monk encourages both women to satisfy his own desires, he commits two offenses entailing suspension. … (To be expanded as in <a href='https://suttacentral.net/pli-tv-bu-vb-ss2#3.2.4'>Bu Ss 2:3.2.4</a>–3.2.36, with appropriate substitutions.) …

Encouraging sexual intercourse to two beings of different kinds