'Mafumafu-san' (Trending with 'Uruha Rushia' and 'Virtual pigs'), 'Rushia and Mafumafu', and 'Engagement Ring' currently make up 3 of the Top 5 trending in Japan.
A lot of it is laughing at Gachikoi which, as funny as it is, is likely to result in said Gachikoi throwing a shitfit.
Japan is not unlike China in that the general public expect an IMMEDIATE response to these things, and the option of 'Lie to them by saying it's a misunderstanding and they aren't actually together' is off the table because they already used that in 2018. So their only REAL option now, without disrespecting the intelligence of their fans, it to admit that they're dating.
Alternatively, Cover COULD risk burning some good faith to pretend it doesn't exist and see if it blows over with little repercussion, which I think is what they're gonna roll with.