Hah?! A love rival you say Eliza?! Both of you and new girl get outta here, Lilith's the genuine OTP material here... The harem tag doesn't have a lot of weight nowadays since I noticed that rarely does it really end as a harem despite the tag. And Lilith waited for this guy for how long?? Likely other characters introduced to join the "harem" would likely just be annoying hang-ons.
Unless of course, for some inexplicable reason, author decides to pander to the idiotic, ditzy classmate archetype...