Share is a term describing the amount of influence a CPU and her formed nation has over a place. The amount of share is influenced by the amount of faith and belief people has over a CPU. In addition to influence, the CPU's powers depends on the amount of acquired share. CPUs can be incapacitated if they have insufficient shares, though this is proven wrong gameplay-wise.
Share acts a gameplay mechanic in Hyperdimension Neptunia, Hyperdimension Neptunia mk2, and Hyperdimension Neptunia Victory. They total shares that can be acquired are divided between the nations of Gamindustri (Planeptune, Lastation, Leanbox, and Lowee) and a separate influence. Each nation and influence has a set amount of share at the start, so it's only possible to transfer and gain/lose shares from each other rather than gaining it from an outside source. The amount of shares a nation has affect the power output of its respective CPUs and may affect events that may otherwise transpire in the story.
Hyperdimension Neptunia
Shares are separated between the nations of Gamindustri and an influence labeled as "Other."
Each nation can gain up to a maximum amount of 100% and of shares and will never decrease below 5% with the exception of Other. Other has a starting amount and a minimum of 0% and can gain an indefinite amount of shares. The player can transfer shares from nation(s) to nation(s) by doing side quests. If the player leaves an optional dungeon, 1% of share from each nation is transferred to Other. If Neptune dies in battle, 1% of Planeptune's shares will be lost permanently. Using the "Try Again!" option does not reverse this effect, and only loading a game before the battle that was lost will resolve this.
Hyperdimension Neptunia Re;Birth1
Shares have very little influence outside of the ending and a few plans in the Remake System.
Shares for each nation and "Other" are gained and lost by doing quests and fighting battles in the Colosseum. Each quest and Colosseum battle raises a certain nation's shares by a listed percentage, and decreases another's by the same amount. The totals Shares will always add up to 100% and none can be lost permanently. If a certain quest or battle would drop a nation's shares below 0%, it will only lose enough to bring it down to zero, and the corresponding gain will be limited to the same amount. To obtain the true ending in Re;Birth1, each nation must have their shares at 20% or more, and the shares for "Other" must be at 0%. Certain plans for adding "Super Enemies" to some dungeons require a specific nation's shares to be at 25% before they can be used. In addition, to obtain the plans for adding Nepgear, Uni, and Rom and Ram, their nations' respective shares must reach 30%. To make the plans, that nation's shares must reach 50%.
Hyperdimension Neptunia mk2
Shares are divided between a nation's main city (local shares) and its surrounding cities, which add up to the respective nation's global shares.
Shares are separated between the nations of Gamindustri and Arfoire (Gamindustri Graveyard). At the beginning, Arfoire has possession of over 70% of the global shares. To be exact, 69.1% belongs to Arfoire, 7.6% belongs to Planeptune, 7.9% belong to Leanbox, 7.5% belong to Lastation, and 7.9% belong to Lowee at the beginning.
Shares can be transferred from one influence to another by doing quests from The Guild or winning battles in Gamindustri Graveyard's Coliseum.
Unlike Hyperdimension Neptunia, there's no way to permanently lose shares. There is no way to transfer shares back to Arfoire once all its shares are taken.
Hyperdimension Neptunia Re;Birth2 SISTERS GENERATION
Shares in Re;Birth2 use an identical mechanic to shares in Re;Birth1, however the "Other" shares now belong to "Arfoire" (ASIC). Certain shares are again needed to unlock and use some plans, as well as recruit come characters. Starting in Chapter 4, Tekken will join the party once Leanbox's shares have reached 30%, CyberConnect2 will join once Lastation's shares have reached 30%, and MarvelousAQL will join when Lowee's shares have reached 30%.
Once Neptune joins the party in Chapter 5, Noire, Vert, and Blanc will join once their respective nations have reached share totals of at least 50%. Starting in Chapter 6, having a nation's shares at 50% will unlock the plan to recruit that nation's Oracle (Histoire, Kei Jinguji, Chika Hakozaki, and Mina Nishizawa). To make the plan, that nation's shares must then reach 75%.
Getting and unlocking the plans for the Oracles only needs to be done once (each) among all playthroughs, as plans carry over in a New Game+. The CPUs and Makers, however, need to be unlocked in each playthrough, as these are not governed by the Remake System.
Re;Birth2 has a total of nine endings, each one dependent on shares, what party members have joined in the current playthrough, and Lily Rank.