Board Thread:Manga/@comment-29463491-20170405151511/@comment-30069705-20170405174421

We haven't necessarily forgotten Historia. But as has been stated, Eren fears what the military might do to Historia if they ever find out how Eren thinks he may have activated the Founding Titan, so he's keeping his mouth shut for the time being for her protection, and it seems he's not even entirely 100% sure anyways. Plus, when Eren touched her while she's still just human, he only got memories. She may need to be titanized for him to get more control of the Founding Titan.

Besides, we still don't even truly know for sure yet if the Reiss and the Fritz really are one and the same, and Historia could be just a Reiss, but not a true Fritz. Maybe the Reiss can help with the Founding Titan to some extent, but in the end, it could be the Fritz that's the real deal and the one that Eren must turn to in the end for full power, which is where Zeke comes into the picture.

If you recall, Frieda Reiss couldn't even properly use the power of the Founding Titan to defend herself and the rest of her family when Grisha attacked. Rod Reiss said it had to do with her not being experienced enough to utilize its power, but he was also a liar in some ways and trying to manipulate Historia. Perhaps the real reason Frieda couldn't use it's power is because she was never really meant to use it on her own anyways due to being just a Reiss, and perhaps a true Fritz would master its power immediately.

Either way, it's Zeke who was said to "hold the key to the story" and give us a chance to "witness the last mystery that lies ahead". I have a feeling that him helping Eren access the full power of the Founding Titan to end the whole conflict is going to be part of it. It could be because he's a true Fritz rather than a mere Reiss. Maybe being closely related to Eren as half brothers can further help with the use of the power. Maybe him being a titan shifter can also help further access the power. It could even be a combination of these things.