The preseason is one of the best seasons of Aibou, and it introduces the characters and setting perfectly. Each episode is 90 mins, so it feels like a mini movie, and each episode is suspenseful, thrilling and surprising. The chemistry between Sugishita and Kaoru is brilliant from the very start. The supporting characters are also very good.
All three episodes are very close in quality, but episode 2 is probably the best, just because of how the tension never stops for a minute, and the ending is shocking.