Lily Rank is a gameplay mechanic that is first introduced in Hyperdimension Neptunia mk2 and is also present in Hyperdimension Neptunia Victory. It measures the level of friendship and trust a character has for another. By raising the Lily Rank between a character, it may affect events in the game and/or unlock certain things like being able to synthesize certain items in Item Synthesis.
Hyperdimension Neptunia mk2
In Hyperdimension Neptunia mk2, the Lily Rank system measures the level of friendship between Nepgear and her companions. Lily Ranks between Nepgear and a character can be increased by having the character participate and win battles, whether the characters are Front participants or Back partners, or seeing certain events with the character in Chirper.
There are five levels of Lily Rank in Hyperdimension Neptunia mk2. The amount of work the player needs to do to increase Nepgear's Lily Rank with another character increases with higher ranks.
Hyperdimension Neptunia Victory
Victory brings back the Lily rank system, but has made a few changes to it. Unlike mk2, where the system only applied to Nepgear and her relationships, it now applies to all characters and their relationships to other characters. Secondly, Lily ranks can only be improved by having one character acting as support to another character. Lily ranks are used in order to access support abilities, make certain items, or use various EXE Drive skills.
Most characters start out with a preset Lily rank with others, depending on their relationship in the story. DLC characters start with a rank of 0 with all characters, the only exception being Hyperdimension Falcom who starts off with a good Lily rank with Nepgear.
Hyperdimension Neptunia Re;Birth1
Re;Birth1 brings back Victory's implementation of the Lily Rank system, and functions largely the same in terms of gameplay. As before, most characters start out with a set value based on story and relationship.
Hyperdimension Neptunia Re;Birth2 SISTERS GENERATION
Though a remake of mk2, the Lily Rank system still functions like in Victory and Re;Birth1 in terms of gameplay. Even then, Nepgear's Lily Ranks with other party members are nonetheless of higher importance, as they affect the ending route taken.
Just as in mk2, Nepgear can raise her Lily Rank with characters by viewing certain Chirper events.