Who is Kobe? Are you referring to Kirby? 

Not sure about Kobe (not even sure who this is, actually), but Katarina and Emma both require completing the sidequest regarding Mario's Villa.  In my playthrough, I successfully turned Katarina to my side, and enlisted Emma's help in having Sofia arresting Mario; this unlocked both characters to be invited during their respective conversations in the Villa.

Milky Coin

You get a coin every time you fill up the container  

Container = Plainview > Farm > Farm > Barn > Harvest 

Spend Milky Coin = Plainview > Farm > Farm > Enter 

Tasha Coin 

You get a coin after winning every game of Dungeon Master in the Comic Store