#oopsie...

Besides the obvious (it’s right on the summer solstice- almost opposite of Junko/Mukuro’s around the winter solstice), let’s take the numbers 6 from the month, and 21 from the day.

There’s a 6 sided die. Add up the sides: 1+2+3+4+5+6. You get 21.

Now imagine there’s a twin, a sibling with the same birthday. You have not one ‘die’, but two ‘dice’. Like the group, ‘DICE’. 

Now we add all the sides of the two dice. Here’s a nifty number: 42.

A few things about the number 42 which are really cool! First of all, it’s ‘The Answer to the Ultimate Question of Life the Universe and Everything’, in reference to The Hitch Hiker’s Guide to the Galaxy, another sci-fi oriented piece. Second, it’s a number that can be associated to ‘God’ and the ‘Universe’ (according to Kabbalah, ‘42′ is the number with which God creates the universe). 

Third... well. Taking from what I’d said before about Ouma and Shuichi having ‘opposite numbers’ associated to them - Ouma having ‘Ni shi (shi)’ as a 2 and 4, with Shuichi’s ‘shini(gami detective)’... ahem, ‘god of death’ thing being 4 and 2 - this cosmic and godly number 42 is associated to both of them as well.

Now for something wild: take Ouma’s birth month: 6. Shuichi’s birth month: 9.

6 times 9 is 42 when done in Base 13, as said in Hitch Hiker’s Guide to the Galaxy. For extra fun- the digital root of 13 is 4. BAD LUCK.