That looks bang on mid-portion tendon, not one of the bursae. This is the classic tendinopathy most likely to respond to an eccentrics programme. It's a not trivial amount of swelling but not uncommon to see this: From here
I've spent an entertaining 10 minutes watching Karate videos, so now consider myself an expert. There seems to be a lot of bouncing up and down on your toes. Increased amounts of this over a fairly short time would be a pretty obvious route to tendinopathy (many climbing analogies). There is also a certain amount of smacking people in the head with your heel, which might not be too clever for the Achilles either, though this could be over-represented in the 10 best Karate KOs
genre thrown up on YouTube.
Usual disclaimers: pay far more attention to someone that has actually spoken with you and examined you.