What is the ruling on naming a newborn girl "Kikyo," which means "Chinese bellflower," and naming a male "Kohaku," which means "amber" or "black gold," which is a precious stone?

A name is a title for what it names and has an effect. Therefore, Islam emphasized choosing and improving names, and prohibited bad names or those specific to non-Muslims. For this reason, we do not recommend naming with this type of name. As for the two names mentioned, if their meanings are as stated in the question, and they are not specific to disbelievers, and do not include a religious prohibition, then there is no objection to naming with them.