Companies seeking initial public offering may, prior to sale, conduct a preliminary book building, and if there are unmet asks after the sale, sell additional shares.
 
Preliminary Book Building
The underwriter may collect asks of the investors in a certain price range prior to the registration of shares by the board with no obligation and binding on the part of the applicants.

If a priority will be attached to preliminary applicants, this should be announced in the notice, the preliminary prospectus, the prospectus and the circular. In that case, the preliminary book building notice has to be announced.

The results obtained from the preliminary book building cannot be used for advertising purposes, and the period of preliminary book building cannot exceed 30 days.
 
Additional Sale
If the quantity of conclusive asks collected in public offering is more than the quantity of shares offered, then in order to meet the additional demand, shares of existing shareholders that have been determined in advance may be put to sale limited to such amounts specified in the prospectus and the circular.  

However, the quantity of shares which will the subject of additional sale cannot exceed 15% of the quantity of shares offered.