Himitsu no Mori no Majutsushi wa Nodoka wo Negau

Shagar is a great hero whose incredible magical power ended a war... Or at least, that's what he used to be known as. Cut to the present day, and Shagar's magic has been sealed away, unable to be used at all. The former great hero spends his days deep in a forest in complete solitude, other than the occasionally visit from Luso. If this rugged mercenary doesn't stop by regularly, Shagar won't be able to transfer his pent-up magical energy outside of his body, which could very well kill him.

When attacked by monsters while gathering water one day, Shagar is saved by the young Fio, who insists on being his disciple! Though Fio has great potential for magic, his true strength lies in his seemingly unlimited capacity to accept Shagar's magical energy. These two might have the kind of chemistry that Shagar has spent so much of his life searching for...

(Source: Takeshobo)