[hyl]

It's not much of a reference but rather a very minor cameo.

Spoiler for spoiler:

When snooping around in Honoka's room, Shun accidently stumbles on a very old picture with someone who is probably his ancestor (because Shun thinks that the women on the left resembles Sana alot) and a certain character from 11eyes crossover

edit:
I am aware that Honoka has the same last name as a certain glasses wearing character from 11eyes, but that is IMO not a good reference to their past games.
And I haven't played other lass games aside from 11eyes to notice possible other cameos or references though