在这部名侦探柯南OVA3：柯南、平次与消失的少年动画片中,春天的某日，柯南和小兰受服部平次和远山和叶的邀请，再一次来到大阪城观光。原本平平常常甚至有些无聊的行程，却因为三个少年的出现而变得乐趣横生。他们是江坂茧美、八木干彦和大泽健太，无论外貌还是长相都与远在东京的步美、光彦和元太极其相似。少年们找到平次，拜托他帮忙找出失踪的伙伴小智。柯南实在受不了平次安排的枯燥行程，于是答应了少年们的请求。众人经过一番推理，决定先从线索之一的大阪环线入手。平次在电车上无意中看到正在执行任务的大泷警官，而这似乎又与当天早上发生的抢劫信用社有关。小智的失踪事件、银行的抢劫案，它们彼此之间究竟有何关联？
A successful detective gets injected with a virus which makes him a 10 year old boy. But as his brain and mind are similar as before he helps his girlfriend's father (an unsuccessful detective) to solve cases without getting known to anyone.
