u/puzzledcheeto

Im gonna post here a quick translation of the text from the CM:

Narration Ononoki Yotsugi

Assassination plan
restart.

The world

"Don't you think this world of fakes should be destroyed, brother?"

Phoenix
Phoenix
Phoenix

"Searching for somone, like a detective story...
Whats with being tired of justice.
Kill your friends...
...Hachikuji, this...
--You should know this, Ononoki Yotsugi...

Fake
Fake
Fake

As the title descibes, this account on X is from a person that assited to the Tanabata event of Monogatari, the text under the date says (roughly, take this as a grain of salt):

"Don't you think this world of falsehoods deserves to be destroyed, brother?" the text uses お兄ちゃん onii-chan, which is the way Tsukihi refers to Araragi, Karen on the other hand tends to use only 兄ちゃん nii-chan. So its kinda confirmed this line is a dialogue from Tsukihi.

Edit: The line was used in previous novel announcements, its not a new phrase.