Ensemble Darkhorse: Reiko is by far the most preferred of the partners. This makes sense, as she represents the Neutral route, which is also the most popular in the series.
Epileptic Trees: On its own, the game doesn't really spawn any, as the whole thing is meant to be self-contained. Once it serves as the cornerstone for an entire Alternate Continuity, however, boy howdy. A ton of this centers around Hazama, such as the question of just how he got the power he did, since nobody else gained such power to shape the "Demon World" like he did just by entering. And he just meant to summon a demon at the start anyway, not suck the entire school to the other side... And where the hell is the actual leader of the Abyss in all this, anyway?...
Then there's the fact that the first "Demon Emperor" form that he fights you with looks an awful lot like Akihiko Sanada's Caesar Persona, and the Demon Emperor seems to come out of him in a manner visually reminiscent of a Persona in later titles... just a Shout-Out from a later title back to If, or?...
There's also the question of exactly how much of the game happens, or is, in Hazama's mind. The idea that everyone was transported there instead of the demon world makes some sense, considering that the ritual Hazama performed probably couldn't have given him the kind of power it did, as well as the fact that Lucifer is conspicuously absent.
Some of these questions are answered in Hazama's Chapter. The Demon God Emperor is actually Zurvan, a demon who tried to overthrow Lucifer and warped Hazama's mind for its own goal. Lucifer can give Tamaki the Ring of Light to free Hazama from its control.
Scrappy Level: The gimmick to the Sloth dungeon is that the students and faculty of Karukozaka High are being made to excavate something. You can help them out a little bit, but in the end you have to wait for a long number of full lunar cycles before you can find what you need to continue. Since you need to move around the dungeon to advance the lunar cycle and this triggers constant random encounters, this takes hours of pointless, directionless grinding. Many players stop here out of sheer boredom. In other words, this level is just the bane of lazy people.
WTH, Costuming Department?: Those blue/green/white striped pants and skirts easily make If's school uniforms one of the tackiest in fiction.