Mr. Kazumasa Yamatani is the company president of IT Enterprises and a big collector of anything having to do with the Three Kingdoms of China. He's a hoarder and only with great reluctance would he ever expose his treasures to prying eyes. When the Dark Shadow go after the scroll he has, he is endangered. Souta protects him with enthusiasm and melts the man's heart (after getting it pounding fiercely) until he realises that even today there are adventures to be had for the joy of it, and that other people's happiness can matter.
Engaging in a little International espionage, this man was selling the Imperial Pearl. Unfortunately, his clients didn't want to actually spend the money. The Boukenger kept them from killing him and he ran off, never to be seen again.
To the right is Shou-kun, who suddenly found himself with a handful of Pearl a heroine asked him to keep safe and a strange, scarey woman in pink chasing him all over town. Though he was ever mindful of lessons learned in school not to talk to or take food offered by strangers, he eventually was convinced of her sincerity and probably, though they never said so, realised she was the heroine who had passed the Pearl into his custody in the first place. It certainly helped that Sakura fought Kaze no Shizuka and the monster to keep him safe.
A random child lost in the Sargess Museum. Sakura had attempted to help him out, but her impatience and frustration scared him and only made him cry louder. They were both rescued by Natsuki's timely arrival. She charmed the little boy and calmed him until his mother caught up with them.
There are things we do. And when we are Professor Jimon Kagawa, those things involve writing books about adventurers that Satoru Akashi just drowned himself in. While the Boukenger were pursuing their adventure with the Salamander's Scale, Professor Kagawa didn't really know why his study came under lizardly attack. Ryuoon retrieved a hand-written diary presumably written by himself before he'd gone reptile, that seems to contain such phrases as "The right hand of one lizard disappeared and fell... dying scale. I didn't ... had felt that a lizard of this dying state ... the lizard was the lizard which I lost" and goes on about this until it says "...all the theory that I thought about was right. I intend to continue testing it..." and made sure to burn it. Professor Kagawa, though, had a sneaking suspicion that Ryuoon was the same person who wrote the stolen diary.
Nameless and as such unremarked he might have been, but he appeared twice. Branded on the back of his hand he is under Gaja's control, being used to pass things preferably kept out of evil's hands. He seems like a fairly innocent salary-man in his daily life.
He, too, was nameless and would have passed unremarked. He seemed to be the leader of the group of treasure hunters Masumi was with as a child. They all laughed when the indignant child told them he would grow up to be the greatest treasure hunter of them all. They didn't survive the laughing long. Yami no Yaiba came to their camp and killed them all, but Masumi dove behind this man, who died in the swarm of Yaiba's 千羽鶴闇吹雪 Senbazuru yamifubuki Thousand Paper Cranes Dark Snowstorm attack.
Wandering into our story is Sereney. Smart, sneaky and lovely, she uses the Boukenger to distract the Jaryu while she collects the treasures of Kaguyahime. Naturally, Souta thinks she's lovely and happily assists her. At the end, when he sees her run off, he catches sight of a bit of gause in her back pocket and can't help but wonder if she is Kaguyahime herself, or at least the source of the legend.
Arriving with more force is Magi, the Old Man of the Sea. He's come to stop Ragi, a younger member of his race, from a disastrous mission to retrieve the new Water Crystal from the heart of a volcano. He's so tired of his people dying that way, it just seems too high a price to pay to return the sea so they no longer live in blind desert.
Of course, there is Ragi. Before and after. A young man determined to accomplish his father's - indeed, his people's - dream. To return to them the waters of their home. They were the people of a legend, of the "City at the Bottom of the Sea". But their Aqua Crystal had been destroyed. The sea dried up and their city was covered in sand. According to the Crystal Scroll, a new one was forming in the heart of a volcano. Ragi carried the shattered crystal of his father when he went out over the desert on his mission. He was determined to get to the crystal at any cost. When Ryuoon rescued him from certain death and offered to give him a body that could survive the rigors of the volcano, he accepted without hesitation. But his people's powers were not compatible with the Dragon power, so he gave up his crystal and allowed it to be destroyed, which would mean he could never live under the sea. Satoru, being an old softie, cast his lot with Ragi and helped him get the Water Crystal, convincing Magi that it was worth this one more try. Satoru also reconstructed Ragi's father's crystal with Magi's help (I think) and gave it to Ragi. He can live beneath the Sea again, though perhaps never in his original form.