At the most he may have clocked 150 kmph, as we can't expect a 17-year old to bowl any faster than this. I think 150 kmph was the fastest ever bowled by U-19 bowlers, such as Kamlesh Nagarkoti. But still, I regard Matheesha Pathirana as a future prospect for Sri Lanka, at a time when they are struggling to find a successor to Lasith Malinga.
Expected this though 150 is still a great speed. His bowling action seems weirder than Malinga's bowling action and observed that he gave a lot of runs and did not take many wickets at all. He needs to improve his lengths.
Japan are not into cricket that much as India is. Cricket is new for them and it is good to see new countries coming out and pushing themselves into this sport. So there is a big difference in both countries play levels.
This is good news. Am a big fan of some of their anime shows like DBZ, One piece, MHA etc and I would love to see them make a Cricket based anime since they already made a couple of sports related anime before.