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誠心誠意， せいしんせいい
1. in all sincerity, with one's whole heart, whole-hearted devotion
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尽くす， 尽す， 盡す， つくす
1. to use up, to exhaust, to run out of
2. to devote oneself (to), to do one's utmost (for), to serve, to work (for a cause)
3. to do to exhaustion, to do completely, to do fully
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に
1. at (place, time), in, on, during
2. to (direction, state), toward, into
3. for (purpose)
4. because of (reason), for, with
5. by, from
6. as (i.e. in the role of)
7. per, in, for, a (e.g. "once a month")
8. and, in addition to
9. if, although
tbd