N5 — outside your level filter
Is said whole, with nothing composed onto it and takes no copula, so there is no paradigm to conjugate.
こちらこそ
kochirakosolikewise; the pleasure is mineN5expression
Related words
Similar meaning
both mean "mine"
Readings and definitions from JMdict, © the Electronic Dictionary Research and Development Group (EDRDG), used under CC BY-SA 4.0; levels from the Tanos JLPT lists.