Sand Castle

is the twentieth episode of Ultraman Taiga.
==Synopsis==
Professor Motomiya is developing a device called "CQ" (Seek You), which can distinguish aliens from humans. She is targeted by a hitman, but someone from her past comes to protect her.
==Plot==
Mystie, from Alien Haze, drove away a group of bullies who were targeting Sachiko Motomiya, and helped her rebuild her sand castle afterward before departing again.
Members watching the city has blackout last week but turned off. As Saku goes to the HQ, he had a little plan for members. He puts a flash drive to see a device, called "CQ". Hiroyuki and Homare met Sachiko, a researcher that she uses CQ to see humans and aliens. Just as Alien Bado El-Ray was about to snipe at her, Mystie jumped at and pushed her out of the way of the bullet, before bringing her to safety. Sachiko recognized and remembered him after taking a quick glance at the marking on his hand, but they had no time to talk as Mystie quickly left the scene after Hiroyuki arrives. Homare went to fight El-Ray, but he called the Giant Ant Terrible-Monster, Aribunta, from underground to take him away, escaping for now.
Hiroyuki tells her that Mystie said to "stay from the estuary." They saw Eneclone's stock prices, that called Zolin Corporation, the shell company. Zolin hires El-Ray to kill her, who was developing CQ that can distinguish humans from aliens through scanning, which Zolin saw this as a threat to him and his cronies. She found Zolin's data that they go outside. Under the bridge, Hiroyuki, Homare, and she try to search persons that she studied as hard as she could and made this machine. 
She saw CQ, reacting, that Homare left except Hiroyuki. Mystie had to meet up with two "accomplices" of his, in replacement of Serpent who was supposed to arrive instead. He had planned to stop the both of them before they could call Aribunta from the ground again to take him away, escaping for now. He went back to Zolin to report to him, but was reprimanded. Later, El-Ray returns, holding Sachiko at gunpoint to corner Mystie, but his plan was ruined by Homare, who was nearby and wanted to capture him after eavesdropping on their conversation. 
Hiroyuki transforms into Titas and was initially able to beat the Terrible-Monster down, until it employed a new tactic: repeatedly burrowing underground and coming up to attack at short intervals. After getting hit a few times, Titas listened to the Terrible-Monster's movements underground and was able to deduce where it would come up next, and suplexed it. He passes a baton to Taiga that performs Thunder Spark using Gorothunder Ring. Despite that, they worked together to defeat the two alien henchmen with Saku's help, but they did manage to summon Aribunta, who was dealt with by Titas. 
El-Ray and his subordinate are defeated by Mystie, Homare and Saku that Taiga fused into Tri-Strium and slashed it numerous times with Taiga Tri Blade. As El-Ray arrested by Saku, Taiga destroying Aribunta with Tri-Strium Burst. Zolin is ratted out and arrested by External Affairs X for exploiting stock prices, sabotaging Eneclone and spreading false information, watched by Kana and Saku that CQ will become standardized equipment. Mystie said goodbye to Sachiko and left to America, reminding her of their childhood encounter once more. As Hiroyuki will take her to the university, they saw a sand castle, built by her as a child in the past.
==Tri-Squad VoiceDrama==
Taiga talks about Terrible-Monster and explains why they are still around.
==Cast==
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===Voice Actors===
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===Guest Actors===
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**Sachiko in Childhood: 
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**Mystie in Childhood: 
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===Suit Actors===
*Ultraman Taiga: 
*Ultraman Titas: 
*Aribunta: 
*Alien Bado El-Ray: 
==Appearances==
===Ultras===
*Ultraman Taiga
**Normal
**Tri-Strium
*Ultraman Titas
===Kaiju===
*Homare Soya
*Pirika Asahikawa
*Alien Bado El-Ray
*Mystie
*Aribunta
*Alien Zetton Zolin