Let's say the word is Touhou and we're still searching for a hero (that was already referenced in the Megapuzzle), so what about Touhou Mario?

This equation is key to finding the answer. The answer to the equation is not the answer I'm looking for however.

The arrow leads to the answer.

This very equation was my thought process a long time ago. In my innocence I didn't consider that the result could be misinterpreted. This equation shows the real meaning behind the result.

Let's recap some of the other clues which may or may not be helpful.
I'd suggest going to the very start to find the answer. But to the start of what?
One of the words in those quotes are the right direction.
Looking further towards League of Legends will lead you no where.

Hopefully this is enough. Either way this has been really fun and MPCS2 will be even better!

Still difficult and therefore good ;-)

So are you looking for cherry, like in pop + cherry?

I'd suggest going to the very start to find the answer.
The starting answer to the crossword puzzled was Modern Warfare, aka Call of Duty.

Modern Warfare + Youmuu's Ghostblade = Call of Duty Ghosts
Season 2 = FPS's

I'm throwing random things to see what sticks.

Not sure how that works out.

That's actually a great idea. But that's not the answer.

If the tables were turned I’d show you no mercy!

Turn tables = DJ
Turn tables, Nigel the Table, flipped tables, turning the crossword tables upside down,.

"Going to the very start" could mean the origin of the ghostblade, which seems to be some Touhou girl from a SHMUP called Perfect Cherry Blossom.

Origin = Games on Origin
Cherry + Nigel the Table = Dinner
Season 2 will be food related.

I don't speak for everyone, but it looks like you overestimated our brainpower.

You really just need to figure out the equation by using the clues you have, especially the ones that are included on the image. After that it should all fall into place.

Doesn't Youmuu's sound good?

Maybe we're looking for a sound-alike.
Anyone know how Youmuu's is pronounced?
Youmu with a single u on the end seems to be Yo-muh, or Yoma.
Youmuu could be Yo-moo, Yo-ma-oo, Yoo-moo, etc.

I'm Nick, pleased to meet you!

Or, as his name is Nick, we could be looking for a nickname for Youmuu's Ghostblade, for Youmuu, for Perfect Cherry Blossom, or Touhou.

The letters from Touhou are in Youmuu's Ghostblade, so maybe it's bizarre anagram time.

I'm pretty sure our princess in another castle.

I tried to solve the equation, obviously to no avail.

Doesn't Youmuu's sound good?
What sounds good? Pop?

I'm Nick, pleased to meet you!
Maybe Nick Cherry?

Pop + Cherry = cherry pop (like the drink)

.. and with a bit of innocence you miss the second meaning ;-)
Which fits to this tip, bzw:
I'd suggest going to the very start to find the answer. But to the start of what?

Now we're getting somewhere!

I'm pretty sure your princess is in another castle on this count.

Cherry pop isn't what we're looking for.

I feel like when this is done everyone will realize that the answer was in front of their eyes the entire time. The result of the equation that is just to clarify.

Well if the result is a word like Youmuu, my native English isn't going to do us much good, either.

If it's a Touhou reference, I'm totally lost.
I only know a handful of older SHMUPs.
And I'm not going to impress anyone with my manga knowledge.

edit:
Something I ignored earlier. The very start of the thread is a quote, and the beginning of that quote is missing. It should be:

Know that if the tables were turned, I would show you no mercy!

So maybe the first blank in the equation relates to "Know that" (no that, etc.).

Since you've exhausted the possibilities here I can confirm that following Touhou will get you no where.

There's no real reason I left out "Know that". That quote does link into the theme though. And as we know following LoL goes no where so perhaps its more conceptual.

I think its about time we draw this thing to close! Of course I won't let you finish that easily though. Someone in fact has to win.