1) Decently 2) Humbly 3) Inconspicuously 4) Plainly 5) Shyly 1) Decorously 2) Diffidently 3) Genuinely 4) In a humble way 5) In a modest manner 6) In a quiet manner 7) In a self-effacing way 8) In an unassuming way 9) In humble fashion 10) Ingenuously 11) Meekly 12) Naturally 13) On a low key 14) Respectfully 15) Sedately 16) Shyly 17) Simply 18) Sincerely 19) Unassumingly 
• (adv.) In a modest manner.
Mod'est·ly adverb In a modest manner. 
[adv] - in a modest manner
with modesty adverb in a modest manner; `the dissertation was entitled, modestly, `Remarks about a play by Shakespeare``