What is Eren's, the main character's, last name?

Yeager

How old is Eren at the beginning of the season?

15

Who are Eren's bestfriends?

Mikasa and Armin

What are the man-eating humanoid monsters attacking the walls and its citizens living within those walls called?

Titans

Where do they come from?

No one knows!

What is Eren's big secret? How is he different?

Without prior knowledge of anyone, Eren is found to be a Titan

Why is Eren's secret such a big deal?

Before Eren, it was not known that humans could turn into Titans

Who else shares Eren's secret? How is he/she different from Eren?

Annie Leonhart is also a Titan but she had prior knowledge of being a Titan and can do things that Eren can't do yet

What is his/her nickname/alias?

The Female Titan

What happens between him/her and Eren?

An epic battle happens between the two because she turns out to be evil

Result?

Annie crystallizes herself in indestructable crystal to avoid death by Eren and is left in a comatose state