He's definitely the most famous and inspiring university runner out there due to what he's done in Hakone. He's from Iwaki, Fukushima, a city partly inside the disaster exclusion zone. He had anemia problems in high school and never really accomplished much, but somehow Toyo's scout found him and recruited him specifically for the 5th Stage. His last race in high school, the National Men's Ekiden, he had a huge breakthrough and thrashed all the big high school stars his age, on live national television. That kind of got some buzz going around his name. His frosh year was great, with the Hakone 5th Stage record and a 1:03:16 half marathon debut win. After the Hakone record everyone started hailing him as a future great in the marathon.
He set his 5000 m and 10000 m PBs (13:48.54 and 28:20.99, certainly good enough to be welcome on any DI team) his sophomore year and set the 5th Stage record again, but he was injured and didn't run well his junior year. He's had a lot to go through this year with the Fukushima disaster and becoming Toyo's captain, but besides the 5th Stage record he set on Monday he had what I think was the best performance of his career at the Nat'l Univ Ekiden Champs in November. With a mildly uphill finish he won the 19.7k anchor stage in 57:48, roughly a 1:01:55 half marathon if you translated the same pace out another 1.4k.
In terms of what his potential is for the marathon, he's got potential to be good, no question. Hard to say how good based on his 5th Stage runs. His record this year was about 1:30 faster than the previous 5th Stage star, Masato Imai, who ran a 2:10:32 PB in Fukuoka last year. That would suggest Kashiwabara might be low-2:08 to high-2:07 material, which would be consistent with what his Nat'ls anchor run suggests relative to other Japanese marathoners' half and full PBs. But who knows? He committed to the Fujitsu team, which produced Atsushi Fujita (2:06:51), and he said on a talk show this morning that he's going to spend his first year there building up his base and then debut at the marathon next year, so I guess we'll be seeing pretty soon.
Personally I think the team psychology Sakai brings to Toyo was a big part of Kashiwabara's success, so if he can keep that positivity in his new environment along with his very impressive mental toughness then he'll have a good chance of becoming great.