What's the source? If it's from an actual comic book, the vast majority of sound effects are still hand-lettered, and my guess is that this has been, too, considering the soft counters that look potentially inked, the varied letter sizes, etc.

It's from a manga, but this scanlation group translated it, so I thought that maybe it could be a font.

http://www.titaniascans.com/reader/content/Akatsuki%20no%20Yona/051%3A%2... (Bigger size)
http://www.titaniascans.com/reader/content/Akatsuki%20no%20Yona/051%3A%2... (Where it's written "Eek" I guess it's the same font too.)
http://www.titaniascans.com/reader/content/Akatsuki%20no%20Yona/051%3A%2... (Also here, "gyah" it's the same font.