After reading this post, it can be concluded that previous reports of the costume merge system in korea. In korea, it was said that merging 2 costume pieces gave a new piece of different look and set bonus, with added bonuses to stats like hp and atk. BUT this is not the case in CN... well, read on to find out the details.
Costume Merging in v173
Firstly, merging in DNCN is 100% success rate, and each process of merging takes one merging tool. The merging tool costs 2980 CC.
After purchase, the tool can be found in the 3rd tab of cash inventory.
Description is similar to Kor version: seasonal and other selected costumes cannot be merged.
Although the description says that, the actual usability of some costumes appear to be different. For example..:
Lighted costume parts in the inventory when the tool is opened can
be used in merging. The arrows in the diagrams show that C-grade, D-grade, christmas set, 1+1 costume set pieces and even the previous tradeable swimwear hat piece can be traded! However, 2011 swimwear set, event free costume headgear and weapons cannot be merged. Basically the ones where multiple parts are represented by one piece of costume, like swimwear body, cannot be merged.
The idea behind DNCN costume merge, similar to potential extractors ._.
As shown, the costume piece you put on the left will be used for its stats and set bonus, while the piece you put on the right slot will be used for the appearance. The end product will have the stats of the left and appearance of the right, or more simply, the stats of the left has been transferred to the right piece. Yes, irine skill is transferred too!!
Original stats of sailor boots.
Product of merging, still sailor boots, but with irine skill and 150 FD set bonus!!
Upon equipping with the new summer set, works!
Note: the new summer set cannot be used together with other set in 2013, unlike some previous sets. The weapon cannot be changed with light weapons to achieve set bonus as well! So, if you still want to equip those light weaps after buying summer set, you have to move all stats of current costume onto new summer pieces... ikr.
TLDR: The DNCN costume merging system is simply a tool to shift the stats and set bonus of one costume part onto a separate costume piece with a different appearance. The system works well to cater to the needs of players who want to mix and match their costume pieces for unique looks and still want the premium costume set bonuses like 150FD and irine skill. It DOES NOT create new stats or costume set bonuses, nor strengthen the character in any way.