To eliminate RNG hate, can't you just 'buy' yuki-chan for +/- 250,000?
Just put 250,001 on green and 499501 on red and 499501 on black + 500 on even and 500 on odd. (or another combination of the 1:2 payouts.)
The method described above does not work. This user tried such a method (250,001 on each of green, red, black, odd, even), and failed to receive yuki-chan on a roll of 1 (receiving 1M and 2 ryo back).
Most likely requires a single prize of over 1M ryo to receive yuki-chan (or she moved…).
one thing may be that you need the 1 mil ryo from a single space… the ways to win i found based on this are to bet 40,001 on 11 (25x pay out giving 1,000,025 ryo); 83,334 on any single number or element (12x payout giving 1,000,008 ryo); or 250,001 on green (4x payout giving 1,000,004 ryo and highest odds due to being 3:13) since you can't bet more than 500k on a single space you can't win 1,000,001+ ryo since red,black, odd, even, high, low would only give 1 mil due to 2x payout at 500k.
The best "Cheapest in terms of Stamina Spent" option is to use 2,000,015 ryo to bet 83,334 on every number and 250,001 on green. That results in a guaranteed 1,000,001+ payout for less Ryo than putting 83,334 on every number and all five elements.