At beginning of the series, Mai despised Naru due to his narcissistic personality and his egoistical behavior despite his good looks. But after she sees Naru smile in her dreams, she develops romantic feelings towards him. Whether or not Naru returns the sentiment is still unknown though, at times hints are given out by Naru himself that Mai's feelings may be requited. One thing is certain about Naru: he cares for Mai deeply.
We understand that this is one of the numerous Naru X Mai moments which imply that Naru cares for Mai even though most of the other times he usualy makes fun of the fact that he is much more intelligent and more capable of doing things than her.