What I Liked: Gives a more detailed background of Yuuki, Inga and Bettenou that was unfortunately lacking in the series. Especially liking the display and explanation of Bettenou and Inga's powers.
What I Didn't: Story-telling and world-building's still a little patchy, and the constant time-skips don't help. At least the episodic nature of the series is missing from this OVA.
Final Verdict: A great prequel that does a superb job of filling in the gaps with Yuuki, Inga and Bettenou. Unfortunately, not much more history is given to the terrorist events that took place in the world of Un-Go and the constant time-skips become tiring.