That look Masami gave to both Aki and Sensei (when she remembered that Sensei lives right next door to Aki, where this new NTR guy has joined as the replacement assistant), and smiled while clasping her hands in a "this might just work out in my favor" way makes me think that her, knowing this new sleazy guy's personality, probably thinks he will notice Sensei and try to steal her away from Aki, thus eliminating Masami's only rival in love and make it easier for her to get with Aki. But, I might just be reading too much into it, though I believe my hunch is strong.
Idc if he NTRs Sensei tho, I like Assistant Masami-chan more than her.