Usually 20% of the total amout of rice is Koji.
Rice should be warm temperature otherwise the mould will stop growing. 
The mould grows by sending feeding tubes into rice, this tube provides enzymes to break the starches into glucose.
Koji mould also provides 
・amino acids, peptide
・vitamins (for yeast)
・lipids and proteins

Koji mould has 3 types, yellow, black and white.
Yellow is usually used for sake because this produces very low levels of citric acid.

For growing koji there are 2 types, spores(種麹) and granulated(米麹).
The mainstream is using spores, however granulated koji is still used for some ginjo sake(tsuki-haze).

If the moisture content of the rice is too high it will be uneven mould growth called nuri-haze.
This koji is ideal for
・Premium sake with full body flavour.

The feeding tube of the mould grows into the centre of the grain, it is almost impossible to use machine for this style.
Below is the necessary conditions to grow tsuki-haze
・low level of moisture content for slow controlled fermentation to develop ginjo aromas
・less amount of koji spores
・warmer but less humid koji room
Lipid of the koji also produces ginjo aroma.

Making Koji
Bringing in (Hikikomi)
(H)Steamed rice is cooled and laid out onto toko
(M)Cooling conveyor

Spreading the spores(Tanekiri) 
・1-3h after bringing in
(H)sprinkle the spore by hand and wrap it with blanket
(M)spray the spore using steam

Re-breaking up(kirikaeshi)
(H)mix the rice again and break the clumps
(M)the rice is broken up by the rotating rollers

(H)Keep the rice to bed(toko, for futsu-shu, honjozo, junmai), box(hako, not for futsu-shu) or tray(futa, suitable for ginjo) for desired style. 
(M) just leave the rice in the drums.

Middle work(Naka shigoto)
・36-33c, rising again to 38c
(H)make the koji shalowly to provide oxgen and evaporate the water
(M)the rotate roller keeps on rotating to redistribute water and heat 

Final work(shimai shigoto)
・higher thatn 38c avoid exceeding 43c
(H)Increasing the surface area to reduce heat and dry the rice
(M) the rotate roller keeps on rotating to redistribute water and heat 

Sending out(de-koji)
・reduced from 38c
(H)Transfer the vessels to cool down the koji to stop the growth
(M)Lower the temperature inside the drum