Why? Hearing only good stuff about him, would love to hear your opinion since you've probably seen more of him than any of us...
Well you have to say that he is a pretty quick player with enough shooting power but depending on the system this is not enough....
For Leverkusen he mostly played as a winger, which demands a lot of defensive work too - especially with the high pressing Leverkusen does.
Last season he scored 11 goals in 30 games which isn't that bad but only assisted three last season (and 7 in all his time in Leverkusen).
I and a lot of others were not happy with his understanding of the game, selfishness and his defending. It often appeared that he just jogged back and didn't really get into tackles and such.
Always got the impression he just wants to score himself than setting someone up or doing the dirty work.
Many Leverkusen fans were surprised that he was still in the starting eleven and it was suggested that it had something to do with the shirt sponsor being LG and from South Korea too (pinch of salt but who knows)
Anyways in the right system or playing as the second striker or behind the striker might be good for him but I have to say that I have seen very little that suggests that he will succeed in the PL but you never know... But my guess would be he would rather become a Kagawa than a hit..(might have jinxed it now)
I think that 30m is definitely too much but maybe under Porchettino he will adapt to the PL and will improve his abilities..