一も二も無く[ichimonimonaku] unhesitatingly
一言二言[hitokotofutakoto] a word or two
一石二鳥[issekinichou] killing two birds with one stone
一二に及ばず[ichininioyobazu] right away
一姫二太郎[ichihimenitarou] It's good to have a girl first and then a boy

うり二つ[urifutatsu] as alike as two melons (two peas in a pod)
黄道十二宮[koudoujuunikyuu] twelve signs of the zodiac
二度[futatabi] again
最小二乗法[saishounijouhou] least-squares method
三十二分音符[sanjuunibuonpu] 32nd note

ヨガの流行[yoganoryuukou] the cult of yoga
亜流[aryuu] bad second
暗流[anryuu] undercurrent
一次電流[ichijidenryuu] primary current
一流[ichiryuu] first-class

溢流[itsuryuu] overflow
渦流[karyuu] swirling current
押流す[oshinagasu] to wash away
横流し[yokonagashi] diversion into illegal channels
横流れ[yokonagare] flowing into the black market