The truth was that Master Roshi had given up on fighting ever since Goku became the world martial arts champion of the Earth. As the spirit of the Turtle Hermit School had been transferred to other powerful individuals, there was no need for him to be in the spotlight anymore. Instead, he preferred staying in the background, watching the achievements of his students, giving them his advice and taking his time reading magazines and watching TV. Master Roshi deemed that it was time for him to give up and leave the rest to the next generation of fighters.
However, the situation showed that his decision was poor. His students ended up in dire situations for more than once, and he was unable to help because he gave up on the road of fighting. The Saiyans, then Frieza and now the Androids. Despite his meaningful teaching, Master Roshi had turned from a major player to a retired veteran. The majority of the Z-Fighters would respect him, but they all knew that he had entered the group of those that needed to be saved and not those who could save. He was unable to assist them in protecting the planet and most importantly themselves.
"Goku... Krillin... Yamcha... Tien... Even you, Chiaotzu." multiple thoughts were passing througn the old teacher's mind. "How could I become this? I was the strongest man on Earth and I have turned into a shadow of my former self... My children. How could I let myself need your assistance to survive? I should be the one who would stand on the line and give up my life for you, not the opposite." he kept thinking with a serious look on his eyes, a look that Bulma, who was around, could not see because of his sunglasses. "If only I kept up with my training, I would be able to use the Mafuba to protect you from any stronger enemies. Now? I have become useless. I can't even come to your aid because I will be a burden! Your enemies will take advantage of me and expose you!" he kept the monologue of thoughts before standing up from the sand of the beach. He slowly walked at the edge of the island, clenching his fists and looking at the sun.
"Damn it!" he gritted his teeth before he took his fighting stance. "From this day and on, I will return to the life of the martial artist. And when I'll be able to keep up, even with the weakest of the children, I will prove my usefulness once again!" he mumbled.
"Huh?" Bulma turned her head, staring at the old master.
"He's way too serious..." Mr. Turtle mentioned while looking at Master Roshi.
Master Roshi sighed as he took off his sunglasses. Then he started moving his hands in the usual way of charging his signature Kamehameha. "Ka..." he started gathering his energy. "Ha..." he gracefully moved his hands. Afterwards, as the syllable of "Me..." was heard, his hands connected, shaping the small parts of energy to a giant ki ball on the old man's hands. "HA!" he launched the wave at the sea as his body buffed, turning him into MAX Power mode. "Goku... Krillin... I swear on my old life... I will one day use the strongest Kamehameha and make you proud of the perverted old geezer." he said, before reverting into his regular form, falling on the beach from exhaustion.
"Choopo..." Master Roshi whispered to himself, realizing he could not move. It had been a while since he had used that technique. "My body got really rusty, after all." he kept whispering to himself.
"Master Roshi!" Master Roshi and Bulma moved towards Master Roshi. "What was that for?"
"That? Oh... With all these events lately, I remembered my youth, I suppose." Master Roshi laughed before putting on his sunglasses again and getting up. "Anyway, where are my magazines? I need to read the news!"
"You, old geezer!" Bulma punched him in the head. "The others are in trouble and all you care for is reading magazines!"
"Ehehe... Bulma, my times are over you know!" Master Roshi replied to Bulma before walking back to his house. A good magazine would be more than enough for him to relax.