Third Return to Pallet Town

When Ash and Tomo got back to Pallet Town, they stopped at their house first. But Delia and her Pokemon weren't in the house.
"Mom must have gone shopping and her Pokemon must have gone with her." Ash said.
Since no one was home, the brothers decided to go to Prof. Oak's lab instead. But when they entered the lab, they didn't see anyone, not even Tracey.
"That's weird. Where is everybody?" Tomo asked.
Suddenly a bang of party poppers was heard. It was Tracey and Mr. Mime. 
"Welcome back Ash, Tomo." Tracey said.
Prof. Oak, Gary and Delia entered the room and so did Delia's Persian, Victreebel, Ledyba, Marill, Beautifly and Delcatty. 
"That was a surprise." Ash said.
"Sorry Ash, but we decided to give you two a proper welcome home." Prof. Oak said.
Ash and Tomo thanked everyone.
Ash handed his plaque of Frontier symbols over to his mom and told her he won the Battle Frontier challenge. He even told them he was going to be a Frontier Brain in the future, but not at the moment because he wanted to continue traveling first. 
"Well I look forward to seeing you as a Frontier Brain Ash." Gary said.
Just then Ash's two Eevee entered the room and they jumped into his arms.
"Hey you two. Miss me?" Ash asked.
The Eevee licked him to say yes.
"Hey Ash." Gary said. "Grandpa told me that you wish to evolve those two into Glaceon and Leafeon right?"
"That's right I do." Ash nodded.
"Well I'm heading back to Sinnoh tomorrow, so I can evolve your two Eevee for you while I'm there." He offered.
Ash was delighted and accepted Gary's offer right away. 
"I take it you want to go to Sinnoh next Ash?" Tracey asked.
"Yes but there's something I need to take care of before I go there." Ash said in a serious tone. "I want to train my aura first."
He explained to Gary and Tracey about the discovery of his aura powers. 
"Oh yes Grandpa told me that you found out you're related to the aura guardian Sir Aaron." Gary said.
"I've heard about this too." Tracey said.
Delia knew it because Ash told her about what happened in Rota sometime after he left.
"Well you see while I was still in Rota, Sir Aaron's Lucario told me to train my aura before he died." Ash said.
He told everyone about Lucario as well. 
"So I decided to train my aura before I head over to Sinnoh."
"I think that's a great idea Ash." Gary said. "When you've got amazing powers it's always best to learn and understand what powers you have in case you have trouble with them."
Tracey, Prof. Oak and Delia agreed.
"Ash while you traveled around Kanto I contacted my friend Prof. Rowan in Sinnoh and told him about your aura powers." Prof. Oak said. "And in Sinnoh there is a aura guardian who can help you train your power. The man's name is Riley and I had Prof. Rowan contact him for me."
"Have you gotten a response from him yet?" Ash asked.
"Yes I got a response from him yesterday." Prof. Oak answered. "Riley said that once you come back to Pallet Town, you must go to Rota and Riley will train you there."
"I understand. So Rota is where I'll go before heading to Sinnoh. I'll head there tomorrow." Ash said.
He then turned to Tomo.
"Sorry Tomo, but you can't go to Rota with me. I have to go by myself in order to train my aura." Tomo felt disappointed, but knew what Ash was doing was important.
"Never mind Tomo." Tracey said. "You can help me around the lab until Ash returns from Rota."
Tomo appreciated the offer and accepted it, 
"When I get back, we'll go to Sinnoh together." Ash told him.
The next day...
Ash was ready to head to Rota alone. He left all of his Pokemon at the lab with everyone else. Tracey and Tomo wished Ash luck with training his aura and Delia and Prof. Oak told Ash to be careful and to always listen to Riley. Ash bid everyone farewell and headed off to Rota.
So Ash had aura training to think about first before heading to another region.