Page 604 - Makino,Tsutusi.DictionaryOfIntermediateJGrammar

iary verb that indicates completion of something about which the
speaker is emotive. (+ shimau (DBJG: 403-06))

I. Toto is crucially different from yatto in that the former often indicates a
negative situation that came about spontaneously, but the latter indi-
cates a positive situation that has been realized with the greatest efforts.
So, every toto in the KS and Exs. cannot be replaced by yatto, except
Exs.(g) and (h).

However, if the final verb is a verb that expresses s.t. positive that has
resulted by human efforts, then yatto can be used but not toto. Note that
the final verbs in [2a] and [Zb] are non-volitional verbs. If the verbs are
volitional as in [2af] and [2bf], both yatto and t6to become acceptable.
In this case yatto and tot6 indicate difficulty in the process and the
sense of accomplishment, respectively.
[2] a. %?H Bd'gkT {97 L: / *L: 3 L: 3 1 %YDB.'ll$@fV 7zo
(I was able to solve a mathematical problem eventually
after working on it for three hours.)
sL T? &hltL?
b. $$LTL~~%~~D~$ET /??~:3 231
{T~L:
$3 fzo
(I finally found a book I'd been looking for at a second-
hand bookstore in Kanda.)
a'. 3@Bk%%kT IT->:, / L: 3 L: 3) RYOBYEB@~~~~L
(I solved the problem eventually after working hard at it for
three hours.)