A number of additional items might be considered:
- energy boost items [ie +30 energy, that can held onto until a more urgent need to gain xp is present, such as daily contest]
- combativity (fist) boost items [ie +10 combativity, that can be held onto until an event]
- discount coupon items [allows you to buy energy or combativity with fewer kobans [ possibly valid for a) a single purchase, or b) a period of time] (probably: "may not be used with other promotions" )
- luck boost items [ie increase random drop rates for girls/equipment/etc for a period of time]
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There could also be additional battles inserted into the story, where if the scene calls for two specific characters to fuck-battle... actually make those two characters do the battle... ie may require leveling up certain specific characters. This could also use some resource as a required input to engage in the battle (energy, combativity, champion ticket, Y$, item, etc)... it could also be done like the champions so if you don't win at your first attempt, you can keep wearing the boss down.