There appear to be three (3) main avenues of deduction. The first one that occurs is from Youtube, the second from Cover and the third from the Japanese Government. If the talent receives a base salary, then it would be subject to Income tax as their income as supplied by a domestic corporation and would fall under Classified Income.
If the salary paid by Cover to its talents is the minimum of 1,625,000 Yen, each Hologirl will earn a minimum of 1,150,000 yen excluding other taxes if they earn literally no Supacha, or anything from merchandise or anything at all.

The problem comes with Super chat, from the point of the payer, it would be a donation, however, it would actually be classed as ad-hoc income, as the amount paid can vary wildly and the money is paid to Cover by YouTube and not the original person who paid the super chat. It sounds like the money first goes through YouTube and is subject to a 30% deduction. This deducted amount is then passed to Cover. Cover reportedly takes a cut for themselves on this figure, presumably according to an employment agreement which would be revised as needed or annually. This likely differs per talent, as larger talents who earn more can afford to have more money deducted without interrupting normal life. Coco provides a number. She claims 50%, however, this is more likely going to be 30% for the smaller talents. Hence why we get differing figures each time we ask. It also explains why Cover prevents dissemination of this figure as to prevent in-fighting or claims of unfairness between talents. In other words, unless we know that Cover Cut, we will not know how much goes to the Holo.

Cover then have a problem as to what to classify the remaining amount as. It is not a donation, as it was paid to them by YouTube as a form of salary. Therefore, it would be sensible, and the method with the least hassle, to classify it as more employment income, subject to Japanese Income Tax Law. This will assumedly be pre-emptively calculated once per month, with an annual total used to calculate a payment of Income Tax.
Therefore, assuming a lower popularity Holo living in Japan:
$100 Akasupa if the user is paying on an anything other than an Apple device.
-$30 YouTube cut ($100*0.3=70)
-$21 Cover cut (70*0.3=21)
This leaves $49 (70-21) as taxable income. Roughly 4900 Yen. After a year, if the total taxable Supacha + minimum salary falls within any of these brackets, income tax payments are made. The minimum salary has already been accounted for, so the values will be subject to:

Up to 1,625,000 yen: 550,000-yen deduction.

1,625,000 Yen up to 1,800,000 Yen: 40% of gross employment income -100,000 Yen. For example, earning 1,800,000 would mean you make a payment of 620,000 Yen.

Over 1,800,000 Yen up to 3,600,000 Yen: 30% of gross+80,000. For example, if you earn 3,600,000 Yen, you will pay 1,160,000 Yen as Income Tax.

Over 3,600,000 Yen up to 6,600,000 Yen: 20%+440,000. For example, if you earn 6,600,000 Yen, you will pay 1,760,000 Yen as Income Tax.

Over 6,600,000 Yen up to 8,500,000 Yen: 10%+1,100,000 Yen. For example, if you earn 8,500,000 Yen, you will pay 1,950,000 Yen as Income Tax.

Over 8,500,000 Yen: 1,950,000-yen payment as Income Tax

Let us take Korone as an example. She is a resident in Japan and will be getting her salary from Cover. With an estimated 104,624,910 Yen in Supacha (With roughly £15,000 earned in one week on average excluding special events*52 weeks with numbers(The site I am taking these data from doesn’t list the entire history so I am extrapolating a smaller bit of data)). YouTube takes 30%, leaving 70,098,690 Yen. Cover then take a 30-50% cut, assuming 40% as Korone is a larger Holo, this leaves taxable Income of 42,059,213 Yen. Under Japanese Tax Income Law, this would mean she will pay 1,950,000 to the Japanese Taxman. Korone receives (40,109,214 supacha +1,625,000 Yen base salary) = 4,141,734,213 Yen, or $39,310,309.54


The situation should not change for non-residents living abroad, as non-residents do qualify for Income Tax if payed by an international organisation like YouTube. In other words. This system will apply for the HoloENs if they live outside of Japan.

tl;dr. Hololive will be fine, Japanese Income Tax rates for high earners are low but the Youtube and Cover cuts screw them over, Korone has earned $365,943.48 in supacha but gets less than 10% of it. It really screws over smaller ones though, who might fall into the 40% bracket.