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[SPOILER-BOX]http://www.bumped.org/psublog/wp-content/uploads/2018/07/Multi-Materials.jpg[/SPOILER-BOX]
Most of the material chip (Rappy lilipa Nyau) have separate storage. You need to tap the top...

https://www.bumped.org/psublog/pso2es-menu-guide/

At organize tab. See 'Chip Grinding'.

Well... It's up to you to trust me or not. And I not recomment this method if you don't have much luck so...(Myself also can't got Rikauteri with my main char. So, I can't test it myself....)
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First. You have to get Rikauteri chip from Rappy Coin scratch or pay for AC scratch. Right now she isn't in this week scratch. But you can walt and prepare some Rappy Coins, by unlock all main story...

You can try farming any floor but it's really rare.

Or try to get Rikauteri chip when she is return in scratch and finish her gaiden quest. She can randomly give the NT one as a gift.

6 chars with around 180 coins and single AC draw for my main, all are PAs and old NPCs. But I dont mind that because if I got Heroines or DB, I might have to kill my friendlist...
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Try rolling with 30 coins at main. All trash.

Then rolling with 1000ac.
[spoiler-box]http://i.imgur.com/LvAhFMA.png[/spoiler-box]