Yesterday evening I found Aka laying on the gravel of his side of the tank. I took him out and let him be in a small dish so he was able to make it to the top for air. But he didn't make it. I am pretty sure it was just natural death. For the past 6 months I noticed he was slowing down a bit.
He was my very first betta. He was with me for 4 years almost. I'll miss him.