Website and data research by 101Leafy.

101Leafy researched the game and worked out how fusion picks its demon. The rules below are the same in DemiKids Light and Dark, and in Hikari no Sho and Yami no Sho. Pick two allies in the calculator to see what they make.

Fusion calculator

Levels start at each demon's base level. Change them to your allies' current levels. Guides are not in the lists, since they only train.

How fusion works

1. Fuse two allies of different races. The race chart gives the race of the new demon. Two allies of the same race cannot be fused, and neither can a Zombie.
2. Add the two allies' current levels, halve the sum (dropping any half), and add 2. The new demon is the first one in that race's result list at or over this level. When the whole list is under it, the last demon in the list comes out.
3. A Good or Evil ally fused with any race but Alt can end in a fusion failure, which makes an Alt instead.
4. Up to 3 magic spells carry over to the new demon. Ally 1's powers carry over too, or ally 2's when ally 1 has none.
5. Guides (Nex, Gef, Kem, Phoenix, and their later forms) are never fused away. A Guide fused with an ally gets stronger and stays a Guide.
6. Link Fuse, between two linked Game Boy Advance systems, has result lists of its own, so the same pair can make a different demon.

Race chart

The row and column are the two allies' races. Red squares can end in a fusion failure.

Result lists

The demons each race can make, in the order fusion checks them, with each one's base level.

Fusion

Link Fuse

Mixed Blood

1. Mixed Blood is under Train Ally. It fuses two different allies to make ally 1 stronger or rank it up into another demon of the same race.
2. Every demon has two Mixed Blood numbers, one for ally 1 and one for ally 2. Add ally 1's first number to ally 2's second. Ally 1 becomes the last demon in its race's Mixed Blood list whose number is at or under the sum, or the first in the list when the sum is under all of them.
3. No new demon comes out when that demon is ally 1 or ally 2 itself, is more than 5 levels over yours, or is under ally 1's current level. Ally 1 only gets stronger then.
4. Two of the same demon make a Pure Blood instead, which makes ally 1 stronger or raises its Rank.

Each race's Mixed Blood list with each demon's number. Link Fuse uses the second list.

Mixed Blood

Link Fuse