Dead or Alive 5 stays loyal to the franchise's roots, providing a roster that includes all DOA favorites, as well as an unhealthy number of waifus. Following an arguably fair monetization model of being free to play, and selling each character separately, it opens up the door to more players - and who really plays with everyone in any game's roster?
It is kind of a letdown though, when you want to play with friends, and you don't have all characters unlocked! The same model was followed by Dead or Alive 6 too though, so I guess Tecmo saw value to it - or maybe the value is hidden by the cost of DLC skins either way! ?
How to unlock Akira: You must defeat Akira during Kokoro's chapter in Story Mode. Directly playable in Dead or Alive 5+, Dead or Alive 5 Ultimate & Dead or Alive 5 Last Round.
How to unlock Alpha-152: You must obtain 300/524 titles.
How to unlock Gen Fu: You must defeat Gen Fu during Eliot's chapter in Story Mode.
How to unlock Pai: You must obtain 100/524 titles.
How to unlock Sarah: You must defeat Sarah during Tina's chapter in Story Mode.