Summon Night: Twin Age (サモンナイト ツインエイジ 精霊たちの共鳴（こえ） Samon Naito Tsuin'eiji Seirei-tachi no Kyōmei (koe)) is an action role-playing game in the Summon Night series for the Nintendo DS. Summon Night uses a party based system of three characters at a time and a fully touch-based control system. The game was developed by Flight-Plan and published by Atlus. It was released in Japan on August 30, 2007 and in North America on June 3, 2008.
- Artificial Stupidity: The partner AI doesn't know how to avoid spikes and poison pools. You must lead them away from those areas.
- Cry Cute: During a night scene with Aldo and Ayn, the later bursts into tears after learning about how humans look down on the Kascuza.
- Difficulty by Region: Non-japanese versions of the game start Aldo and Reiha with boosted money, skill points, items, and pre-learned high-ranked skills.
- Fantastic Racism: Humans are described to generally look down on the Kascuza. Additionally, Nassau isn't very friendly to most of the humans he meets.
- Guide Dang It!: The game never mentions tells you that characters are invincible while they are casting. Leading many players to wonder why none of their attacks are able to damage bosses that can cast skills.
- Humans Are Bastards: What with the capturing and exploiting of Summon Creatures and all.
- Like Brother and Sister: Aldo and Reiha, despite him being a Summon Creature summoned by her. However, they were raised as brother and sister for the past seven years. Can be subverted to Not Blood Siblings depending on the ending you get (and how you interpret them).
- Little Bit Beastly: The Kascuza have animal-like tails. Most humans call them demi-beasts, a name Ayn and Nessau are not fond of.
- Relationship Values: Every character besides the main character has a support rank measuring this. At the end of the game, this determines the ending you'll receive.
- Tech Tree
- The Glomp: Aldo throws himself at Reiha early in the game, after finding out that she's been fine after they were separated.