Poco every time it reaches the level limit (30, 40, 50...100) will need to upgrade rank to be able to continue to level up (For example: Poco when reaching level 30 needs to upgrade to be able to continue to increase. level 40). When the level limit is reached, the ingredients to upgrade the poco are PocoLove token, 1 poco of the same type and luck. The higher the poco level, the lower the upgrade success rate will be. However, even if you fail to upgrade, you will only lose materials (Doesn't affect your poco).