Jessica,
If you are showing your rabbits I don't know of any breeds that recognize the otter "at" combined with the Japanese "ej" gene.
Usually the tri color rabbits are bred with each other and red since they carry the more recessive "ej_" or "ee" combinations.
If your otter carries normal extension "EE" and "BB" for black then you will probably get blacks and may get black otters. You could also get chestnut/agouti if the tri carries "A" agouti. But at least half of these kits would be carrying the "ej" gene,even if you didn't see it, and it would be showing up later in places you might not want it.
Since your otter has thrown REW this means she carries "c" which is hidden by her "C" full color gene, and if the tri also carries "c" then you could get REW.
Oh yes, and you can get broken of whatever color because the tri carries the "En" gene.
If she were my doe, I would probably breed her to another otter or even a normal agouti or self rabbit, basically ANYTHING that I had that WASN'T tri. Then I would use my tri buck on anything that DIDN'T carry otter, assuming I didn't have any red or harli/magpie does to breed him to.