YOU SAID:

even though he was sleeping in his house

INTO JAPANESE

彼が家で寝ていたとしても

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even though he was sleeping at home

INTO JAPANESE

家で寝ていたにも関わらず

BACK INTO ENGLISH

even though i slept at home

INTO JAPANESE

家で寝ていたのに

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i was sleeping at home

INTO JAPANESE

私は家で寝ていた

BACK INTO ENGLISH

i was sleeping at home