While MC was hanging out with his friend who was "treating him" because he broke up he said that he felt bad for "lying to him", while when they "broke up" the words "break up" were highlighted in red (right after saying she didn't want to break up in black), just as "the truth" was highlighted in red a few episodes back.
The narrative also avoided any mention of his love life, or girls in general during the "break up" period.
Context suggested that they were lying about the break up, and still going out in secret. Pretty well signposted in my opinion, and wasn't surprised when she showed back up.