Eren’s father, Dr. Grisha Yaeger, is the one person who knows the answers to the mysteries surrounding the Titan’s emergence and existence. Accordingly, the secrets of the past were just behind the basement door of the house of Eren’s father and it is possible that the Season 2 might explore that plotline.
There are also reports going around that the upcoming second season will also feature a love triangle happening in Season 2 involving Levi, Mikasa, and Armin.
But there are also rumors saying that Mikasa will be involved in a romantic situation in “Attack on Titan” Season 2 but there is still no confirmation as to whom she might hook up with.
It has also been said that the love story of Eren and Krista that began in Season 1 shall continue in the second season of the hit anime. Interestingly, there are also rumors saying that Krista may actually be the reason for the death of Eren later on.
However, all these supposed plots and subplots for “Attack on Titan” Season 2 are mere fan speculations and should be taken with a pinch of salt.
“Attack on Titan” is based on a manga that was written and illustrated by Hajime Isayama. Earlier reports have been saying that the reason why Season 2 of “Attack on Titan” is taking a long time because the anime wants the manga source material to move ahead by at least four story arcs before the TV series starts production.