What are the conditions for child train tickets? Can young children ride for free?

Train fares in Japan are typically structured as follows:

• Adult (12 years old and older): Individuals aged twelve and above are charged the full adult train fare.
• Child (6-11 years old): Children aged 6 to 11 pay the child fare. On JR trains, limited express, and seat reservation fees are also discounted, while green car fees remain at full price.
• Young Child (1-5 years old): Up to two young children, aged 1 to 5, can travel for free in the non-reserved seat cars when accompanied by one adult (eg: two adults can travel with up to four young children for free). Any additional young children will be charged the regular child ticket fare. The child fare applies to all children (0-11 years) if they occupy a reserved seat.
• Infant (less than 1 year old): Infants travel for free unless they will occupy a reserved seat, in which case the child fare applies.

Furthermore, most JR Rail Passes typically provide a discount for children aged 6 to 11.