There are two usages for this tag on pixiv, and each will be explained.
Mou Nani mo Kowakunai (もう何も怖くない)
See also : Flying Chair
See also : Brave Song
See also : Mou Nani mo Kowakunai, Kowaku wa Nai
Spoiler Warning: Spoiler details may follow.
The tag was first used to describe a scene from Angel Beats! episode 5, where the chairs are equipped with an accelerator/booster without reasons explained. It was quite impactful, and many jokes and parodies were made as a result.
One of the reasons why this phrase is used is due to that specific line being actually a part of the lyrics for the ending theme song Brave Song.
Later in Mobile Suit Gundam 00 -A wakening of the Trailblazer-, the phrase itself was actually a song name for Mou Nani mo Kowakunai, Kowaku wa Nai, sung by Chiaki Ishikawa, which played during the scene where Andrei Smirov died fighting ELS. Some were touched by that scene and many fanarts are produced for the character itself.
It is also assumed that the flow of the direction in that scene itself is what triggered that scene in Angel Beats! to be labelled under this tag, considering they both have similarities :
- Both songs played are emotional songs.
- Both are played in during a scene, the only difference is that while both are emotional songs, one is used for gag purpose, and the other is used for desperate situations.
For this tag, the proper usage for it would be もう何も怖くない or もう何も怖くない、怖くはない, depending on which it is used on.
Mou Nani mo Kowakunai (もう何も恐くない)
This tag was first seen as an episode title for episode 3, (Interestingly, it is also a doujin event of the same name).
This quote was first heard when Mami Tomoe was fighting happily (close to the verge of tears) after realizing that she was no longer alone after being told by Madoka Kaname that they would fight together as a Puella Magi.
It was made famous because it's a shocking death flag event for Mami Tomoe. Since it was made an episode title, and she died after saying that quote, it isn't surprising that this quote was made famous by the fans.
For this case, the kanji used for anything that is Mami Tomoe related (especially with Charlotte) would be "もう何も恐くない".
The difference between the two, while its pronounciation and meaning are entirely same, would be kanji used for the tags.
One uses 怖くない, while the other 恐くない. Both are same in meanings, but the kanji used is different. It is also common that the usage itself sometimes overlapped each other, creating misunderstanding sometimes (even some Japanese are confused).
However, the difference in kanji used also means that the usage for either tags are also different depending on which tag is used on.
In Puella Magi Oriko Magica, Mami Tomoe defeated Charlotte alone without dying.
The death flag itself became invalid because the flow of the story is entirely different from the main series itself. Hence, it is assumed that "If you make friends on that certain place, you're on for a death flag".
"What the heck!?" would be the right reaction for this...
Puella Magi Madoka Magica
Just make that canon already
Mami-san Rescue Team
Mobile Suit Gundam 00 -A wakening of the Trailblazer-
I'm Not In Pain Anymore
もう何も怖くない: Contained similar situations for other anime.
もう何も恐くない: The appropriate usage of kanji for Puella Magi Madoka Magica's episode 3 subtitle.